Q. Three years ago I met a man who was separated from his wife, and we've been living together ever since. She has custody of his two daughters, 5 and 8, and we see the girls once a week, sometimes for an overnight.

The mother is a bitter, vindictive, emotional, unstable woman who will stop at nothing to get revenge on her ex-husband. She seems to enjoy causing pain -- even to her own children -- and counseling has never helped her. When she doesn't want the children to see their father, she tells them that he doesn't care about them, doesn't love them, etc. We're worn out from going between the police and the courthouse to get visitation enforced.

When we went to the girls' dance recital, she screamed and cursed me (I made no reply), and then had words with my friend's mother and punched the arthritic old woman in the face!

She comes from a lot of money but spends it all on herself, and dresses the children as poorly as possible when they visit us, which makes it embarrassing to take them anywhere. If we buy them clothes, they take them home and we never see them again, and if we keep the clothes here, the girls cry because they want to wear them to school.

Now here's the corker. She was recently arrested and jailed for possession and distribution of cocaine and is out on bail until she is sentenced, which may take one to two years. We're very worried about the safety of the children and are trying to get custody, but she can afford high-priced lawyers, and we can't afford a lawyer at all. The father makes a modest income and I can't work now because of health problems.

How do we cushion this situation? What role should I play? Should I tell them the truth about their mother or wait until they're older? (She has told them that she's going to jail which horrifies me.) Should we be fairly strict in our discipline or treat them with kid gloves? I long for clean solutions to a sloppy situation.

A. The welfare of the children is, of course, your big concern. They need you to tell them, over and over, that you and their dad love them completely, that you'd be delighted to have them with you every day and every night, and that you will always be there for them. Like all children -- particularly those whose parents die or divorce -- the girls must be very frightened of being abandoned, but they won't want to invoke the gods by talking about it, or to sound disloyal to their mother.

They won't want you to talk about her either, and you shouldn't. Whatever her problems, she's the only mother they'll ever have. Although her behavior must make you wild, she sounds desperate, and desperately unhappy. With or without cocaine, she is a crippled woman and you can't expect the lame to run with the lithe. The more compassion you can develop for her, the more energy you will have to give to her children. They need fairly firm limits, of course, since this is how children learn to be civilized, but high expectations only work if you give them an equal measure of respect.

Children have the right to say what they think -- in a mannerly sort of way -- and to get plenty of hugs and kisses. Forget about spankings, however. They shouldn't be necessary at 5 -- if they ever were -- and certainly not at 8, when children are so conscious of their dignity.

You mustn't let the girls think you use clothes as a weapon, even though their mother does. Keep their ragtag clothes well-mended, and give each daughter two or three nice school outfits to take home, and another two or three outfits to keep at your place. This should be affordable if you shop at a classy thrift store, like the Junior League, or a good consignment shop. By putting your pride in your pocket, the girls will not only be well-dressed, they'll learn one of life's great lessons: It's better to buy first class and second-hand, than to buy new things if they're going to look cheap or fall apart.

You and your friend will also profit from weekly Nar-Anon or Al-Anon meetings, so you will learn how to deal with addictive personalities and how how others handle custody and money problems in their families. This may seem like a stretch for you, but it's not. Though your friend is divorced, his ex-wife is tied to his family because she's the mother of his children, and whether you're married to him or not, you've become part of this family.

You'll also want to check out "The Ex-Factor," a fine post-divorce handbook by Bernard Clair and Anthony Daniele (Donald Fine Inc., $17.95). Written by two lawyers, its clear advice and sample legal forms should help your friend prove to the court that his children would be better off with him -- the key to any custody modification. Certainly any proof of the mother's drug abuse would be in his favor -- even before she goes to court on her felony charge -- but the judge might like it better if you and your friend were married.

You'll do best if you let your friend handle this appeal while you stand by and stand fast -- and say your prayers. It sounds like everybody could use them.

Questions may be sent to P.O. Box 15310, Washington, D.C. 20003.