I can really relate to how you feel about your mom. My biological father doesn't want to know me. When I was younger he sent me birthday cards but they stopped when I was 15. I called him once before I moved from Colorado to California (he lives in CA) thinking maybe he's want to hang out sometime, but he didn't. I haven't seen him in four years now. But you know what? I've learned that I don't need someone like that in my life. If he doesn't care, that's his loss. I have people that love me in my life, and I try to focus on that. It must have really hurt when your mom said "I love you" to a complete stranger. Maybe its easier for her to say to someone she hasn't seen or has less history with. Even if talking to her about won't change anything, I think you should tell her, just to get it off your chest you know? Then it might be easier to move on. I hope everything works out.