Dear Abby:ÌýWhen I was 16 and my sister "Daisy" was 18, I found out she was in a sexual relationship with my boyfriend, "Tyler," also 18. I broke it off. She then asked if I minded her dating him. I'm sure I said I didn't, but I thought, "Why ask? You were already having sex with him." He and I hadn't. Tyler and I remained friends through the years. He was my first love.ÌýThat episode shaped my dating relationships going forward. It took years for me to learn to trust again. Years later, I asked Daisy why she'd done that, and her response was because she could. We enjoy each other's company as long as I don't let the past into my consciousness.ÌýHow do I let this go? Saying anything may make things worse —Ìýbut it really hurts that she betrayed me and never once offered any indication of an apology. —Still Matters in North CarolinaÌý

Dear Still Matters: Daisy and Tyler both betrayed you. What they did showed a distinct lack of character on both their parts. But this is who they are. You and your sister may enjoy each other's company, but do not think that the core of her —Ìýher character —Ìýhas changed. That she hasn't apologized for hurting you, and her answering you in such a flip manner, should serve as a warning about how selfish and insensitive she is to this day.

Dear Abby is written by Abigail Van Buren, also known as Jeanne Phillips, and was founded by her mother, Pauline Phillips. Contact Dear Abby at DearAbby.com or P.O. Box 69440, Los Angeles, CA 90069.