Opinions

Dear Mrs. Riches:
My sister has hit hard times. She has perpetually bad luck, a bad choice of boyfriends, and lousy credit. She's asked me to help her out by co-signing on a car loan and promises that she wouldn't dare do anything to jeopardize my stellar credit rating. I've always read that you shouldn't co-sign for anyone, but I feel incredibly selfish saying, "Sorry, I don't want my boat to sink with yours." Because this comes up in every conversation we have, I have started avoiding her. I am feeling terrible about that, too. Got any words to the wise for someone struggling to do the right thing?
--Sister Selfish