Q.I made a decision that was right for me as a parent, but apparently not as a daughter, and now I don't know what to do.

Seven years ago I let my troubled 19-year-old sister live with me because my parents were at their wits' end. I found that she was into heavy drugs and binge drinking and wouldn't work or go to school, so I spent many hours giving her encouragement and advice -- trying to be her friend as well as her sister.

During this time I married, became a stepmother to a small son and worried that my sister might be a bad influence on him, since he lived with us most of the time.

After three years I had to put my family first, so I asked her to leave. She immediately moved back to my parents' house, where she continues her self-centered, irresponsible lifestyle.

I've kept in touch with my parents since then -- although our conversations are often strained and awkward -- and I've told them that they don't need to choose one daughter over another. I also said that I'd like to see them but not my sister, because of her behavior. Our visits became infrequent, but recently my parents engineered a surprise reunion for my sister and me. When I saw her, I simply turned around and left because I couldn't have my 10-year-old stepson and our new baby in a house where there might be drugs.

I called my parents later to talk, but they said that I should stop being mad at my sister and that they would "get back to me later."

That was four months ago and I still haven't heard from them.

I've tried to build a better relationship with my parents for many years and feel terrible about giving them up. Why don't they want to see their grandchildren grow up? And how can I possibly get over this loss?

A.If the separation is permanent, you probably can't. It always hurts to give up those we love.

But do you have to give up your parents? They didn't call you as they promised, but you can be the one to call them and you should, for they need your support even more than you need theirs.

Your folks have worked hard to rear their two daughters, only to watch one of them succumb to addictions. Some parents get tough with a child on drugs and tell her to get out -- especially if she is in her twenties; some use all their money on treatments that might help her; and some, like your parents, take her home because that's the only way they know to try to keep her safe.

Your mom and dad are doing what seems right for them, as parents, and they won't change until they simply can't stand their daughter's behavior any longer.

Your sister won't change either, until she can't stand her own behavior anymore. And then -- if she's smart -- she will join Alcoholics Anonymous or go to the Salvation Army to be detoxed. These two organizations have probably helped more people get clean and sober than any others, but only if the addict is ready to change.

You made a great effort when you took care of your sister for three years, but good advice is extremely hard for an addict to follow, and there's no point in giving her more of it. Nevertheless, you can be nice to your sister when she's behaving herself and keep yourself -- and your children -- out of her way when she's not. And don't worry about your baby and your stepson getting into her drugs because she's going to hide them. Addicts don't like to share their drugs.

Even if you won't see your sister, on any terms, you can still see your parents. If you want to talk about your sister, invite them to an Al-Anon meeting, so the three of you can meet other people who have to deal with alcoholics. You may learn new approaches that will work better with your sister.

Or just invite your parents to the movies, or ask your mom to help you shop for a dress or your dad to set up your new grill.

Don't expect them to ask you to visit, however; they know you'll be uncomfortable if your sister is around or perhaps they simply want to get out of the house. Whatever the reason, be compassionate; be generous with your time and be kind to your parents. They'll feel better and you'll feel better, too.

It won't be easy, but you won't regret it.

Questions? Send them to advice@margueritekelly.com or to P.O. Box 15310, Washington, D.C. 20003.