Dear Prudence,
My stepsister and I grew up together from the age of 10, and I consider her a sister and a friend. She is smart, talented, charming, and pretty. She’s also loving to her people and is big on being there with practical support when things are hard for family or close friends. She’s also a serial cheater and “other woman.” It seems like she’s only interested in men who are in relationships. It started in our teens and I always hoped she’d grow out of it from the consequences if nothing else, but nothing has changed. When I’ve talked to her about it before she just brushed me off and said she’s in love and that it’s all worth it.
We’re in our late 20s now and she’s actively pursuing a guy who is married with a new baby, and her boyfriend understandably broke up with her when he found out. I can’t reconcile this with who she is in other ways. She’s hurting people. Her parents seem to have an implied agreement never to bring it up, and her friends have tried and failed. My brother says to leave it alone but it really bothers me that I’m close with someone who repeatedly does this. How do I have a more persuasive conversation with her?
—Sister, Sister