DEAR ABBY: Today was my son's fourth birthday. I gave him a party. Some of the children who came were dropped off by their parents.

One of the boys started grabbing my son's gifts and opening them. But the real trouble began when my mother grabbed him by the arm and pulled him roughly away. This happened twice before my husband could make it across the room and tell Mother to stop it immediately.

I am very worried about my mother. She's 64 and seems to be losing her mind. Her displays of nervous and strange behavior are increasing. Her mother, my grandmother, was a paranoid schizophrenic, and I have often believed my mother might have some type of psychiatric condition.

How do I tell her she needs to talk to someone before this escalates further? I allow her to baby-sit my son for short stints only, and now I'm questioning any further "alone time" at all for them. She calls me constantly, insisting that she wants to see him. Is there an easy way to tell your own mother that you think she is close to "losing it"? If I'm going to gear up for the conversation, I want her to take me seriously. Thank you for your input. -- WORRIED DAUGHTER IN DENVER

DEAR DAUGHTER: No, there is no "easy way." Do you have siblings? Does your mother? Does she have any close friends who also might have noticed her bizarre behavior? If there are, talk to them and get examples.

It might be better if you and your husband approach your mother together. Tell her you are very concerned about her mental and physical health -- and give her chapter and verse about why. Then offer to go with her to her doctor for a complete physical and neurological checkup. If she refuses, remember that you have an important bargaining chip -- your son. Under no circumstances should he spend unsupervised time with his grandmother unless you are absolutely certain that it's safe for him to do so.

DEAR ABBY: My husband, "George," and I have been married 22 years. We have four teenagers. Five years ago, we decided to leave the West Coast and move back east to be closer to family.

George moved first. The children and I stayed behind until our house was sold and the school year had ended. We commuted as often as possible, but commuter marriages are never easy.

During our separation, George had an affair with a woman, and she became pregnant. A paternity test confirmed that he is the father. George was very remorseful, and we decided to save our marriage. He promised he would never see the woman again, nor would he have a relationship with the child, who is now 4. (He pays child support through the woman's attorney.)

Recently, she has begun breaking her part of the agreement by sending photos of the boy, with occasional letters about his progress. Abby, if our marriage is to survive this affair, there must be absolutely no contact. I don't want my children to know about this child, or my family to suffer further. What should I do? -- ANONYMOUS WIFE IN THE EAST

DEAR WIFE: I understand your feelings, but I am not sure they're realistic. It may not be possible to keep knowledge about this half-sibling from your children indefinitely because there is no guarantee he won't show up one day asking for answers -- which he is entitled to.

Has it occurred to you that the real "victim" in this mess is the child, and not you? You may not want to hear this, but my advice to you is to open your heart, recognize that the boy is a reality that should not be ignored, and relent.

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DEAR ABBY: When my beloved Mama died early this year, she left behind hundreds -- if not thousands -- of dollars worth of various medicines.

My sister and I called every hospital, shelter, clinic and aid agency we could think of, but not one could give medicine to people unless it had come directly from a pharmacy. Finally, someone suggested that we call our veterinarian.

Voila! It turned out that many of the gauzes, tapes, antibiotic and antihistamine creams, pain patches, pills, inhalers, glucose regulators, collection pans, gloves and other miscellaneous items could be used on animals!

Mama would be so pleased to know that we found a good use for her old meds. -- IN MEMORY OF MAMA

DEAR "MEMORY": I loved your idea, so I ran it by the California Veterinary Medical Board, which also thought it was terrific. They explained that certain medical supplies such as gauze tape, collection pans and gloves are welcome donations.

However, numerous state and federal laws prohibit the transfer of prescription or controlled drugs. So antibiotics, antihistamine creams, pain patches, pills and inhalers must be disposed of in compliance with whatever laws and regulations are in place in each state, because they can vary.

DEAR ABBY: When I go out to dinner with men, they usually pick up the check. On occasion, I will insist on reciprocating by buying their meal.

When I go to lunch or dinner with girlfriends, I typically like to pay. I am by no means wealthy, but I'm not struggling with finances either. My problem is one girlfriend in particular who insists on splitting the check. I have always thought that was tacky.

I know the obvious solution would be to let her pay every other time, but she isn't in a position to treat at some of the restaurants we go to. Am I being overbearing? Or is my girlfriend too old-fashioned? (I'm 24 and she's 62.) -- PICKING UP THE CHECK IN CALIFORNIA

DEAR PICKING: Splitting the check isn't tacky; it's common practice. Sometimes the "burden of gratitude" can grow heavy, so instead of arm-wrestling your friend, eat at a less-expensive restaurant, let her pull her own weight, keep her dignity and pay her half of the bill.

DEAR ABBY: My live-in boyfriend "Gary's" attitude did a complete "180" after we moved in together. He went from being nice and wanting to go out and do things, to spending all the free time he had watching television. He is also not nice to my 7-year-old son.

Because the boy lives here, I have given Gary one year to change his act. Is that too long? I'm not sure I want to continue this relationship, but I can't afford to live on my own. -- DOING POORLY IN PROSPERITY, PA.

DEAR DOING POORLY: Yes, a year is too long. By then, your son may have emotional issues that will cost a fortune to fix. Tell Gary you expect an immediate attitude change or the relationship is over. As to how you will afford to live on your own -- think back to what you were doing before you met him. You got along without him before you met him, and you're going to get along without him now.

What teens need to know about sex, drugs, AIDS, and getting along with peers and parents is in "What Every Teen Should Know." To order, send a business-size, self-addressed envelope, plus check or money order for $5 (U.S. funds only) to: Dear Abby, Teen Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included.)

DEAR ABBY: My sons are on a football team with a group of young men I love dearly. They spend quite a bit of time at our house, and this has become almost like a second home to a lot of them.

My problem is I am married for the second time to a wonderful man whose name I adopted. My children have a different last name than my husband's. My sons' friends (bless their hearts) always address me by my boys' last name, "Mrs. Jones," and they have even called my husband "Mr. Jones"!

I know they mean no disrespect, but I'm trying to find a way to fix this without making a big deal out of it. Can you help us? In this day and age, I'm sure it happens a lot, and many other men aren't as understanding as my husband is about it. -- EMBARRASSED IN NEVADA

DEAR EMBARRASSED: You and your husband should have corrected the boys the first time this happened. The next time the "team" visits and one of them calls you by the wrong name, smile and say, "I probably should have told you before, but Mr. Jones was my former husband. Please call my husband and me Mr. and Mrs. 'Smith.'" If it's said pleasantly, I'm sure it will upset no one.

DEAR ABBY: I am a 14-year-old teenager who likes to baby-sit. I'm a hard worker and keep the children easily amused.

One of the families that I baby-sit for has a difficult child who is rather bratty, but I can control him very well. Recently, when they paid me, I noticed the amount was less than what I usually get. It is not the first time this has happened, and I have a feeling it won't be the last.

How do I tell this family they are underpaying me? And should I drop them? -- OVERWORKED AND UNDERPAID

DEAR UNDERPAID: The next time you are asked by the family to baby-sit, remind the parent that you charge so much an an hour. Explain that you are saying this because you were not paid the full amount the last time, and you will expect to have the balance added to this bill. If the parents are cooperative -- fine. If not, you have every right to drop them as customers and let them amuse their own "difficult, bratty" child on a night when they'd rather be doing something else.

DEAR ABBY: When I finally summoned the strength and fortitude to leave my abusive husband, I received the blessing of anonymous help, which was a tremendous comfort. The hugs and "Let me know if I can do anything" comments were thoughtful and no doubt heartfelt, but there was nothing that compared to the relief of coming home and finding a sack of goodies outside my door, or a gift card to the grocery store in my mailbox.

One angel-in-disguise sent me and the kids amusement park tickets, which thrilled us all. Another unknown Samaritan mailed me 50 $2 bills. Every time I pulled one out of my wallet those first scary days of trying my wings, I was touched by the underlying message, "You are not alone." -- GLAD I MADE IT IN CINCINNATI

DEAR GLAD: It appears you have some very practical and pro-active "angels" in your life. I'm printing your letter because I often receive questions from people wondering what they can do to help a friend who is in crisis or grieving -- and your letter is filled with practical ideas on ways to be supportive. Thanks for the "upper."

To order "How to Write Letters for All Occasions," send a business-sized, self-addressed envelope, plus check or money order for $5 (U.S. funds) to: Dear Abby -- Letter Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included in the price.)