My ex is still calling me and telling me she wants to casually go out. Even though she is dating another guy.?

I am 20 years old, and my ex and I dated for 13 months, and were very happy together. She got very comfortable around me and the nagging and such ensued. After a while I felt that she wasnt treating me well, and after an unprovoked fight from her, I decided I wanted a split. After about 2 weeks she got asked out by another guy, and she acted like she was really happy . A full month after I broke up with her I went back to her and told her I would like to take things slowly, and she gave me the old "I just don't want a relationship right now". So, I decided to try to move on. During the time she was with this other guy, she made every effort to hook up with me (sometimes we did) and try to see me, and she calls me a couple of times a week. She tells me that in order for things to work I need to "show some effort" for her, during which she is going out with this other guy. She tells me she doesn't really like him that much, and yet they have been going out now for a couple of months. I am wondering if their is a point in me trying at all, or if she is just being selfish.