I have this weird attraction, what do I do?

Last month I met a beautiful girl at bar. I normally don't go to such a youthful type of bar, but I decided to anyway, as I was celebrating a big promotion at work. I saw her and couldn't keep my eyes off her. eventually I went up to her and asked if I could buy her a drink. She complied, and we made a little small talk and we ended up making out a little later. The weekend after I ran into her at the mall after I hadn't talked to her for a while and she was with a woman that I used to have a long-term relationship with. I tried to avoid them because the relationship ended pretty nasty, but she came up to me and introduced me to my ex. The next thing she said blew my pants off. Apparently My ex was her mother. And then I thought about the night making out with her. It's even worse because the attraction didn't go away. I don't know what to do. Help!