Should I accept this girl or not?

Keeping this very short. Appreciate if you read it cause it's bothering me. 

I've starting meeting this girl about one month ago. She's nice and everything. But I found that she had this boy that she was chasing for 2 years, but he was only there to **** her. She is saying that she didn't have feeling for this person and that they stopped talking to eachother approximately one month ago, which is when I started having contacts with her. But what I was wondering is how did she not have any feelings for him if she kept going back to him even though he was only using her for sex? 
This is obviously something y'all can't answer that easily, but like in general what do you think. I also asked her if I was a type of rebound guy that she was after, and she stated that I wasn't. Having so much anxiety now cause I don't know what I want. I want the girl, but I don't know how I feel about her leaving the dude she was chasing for so long so abruptly and then started talking to me. If you have any advice please help me I'd appreciate it so much.