The EX That Won't Go Away!

Side 1 says... I've been seeing Jim for a couple of months now. We've gotten really serious and I'm really falling for him. The only problem is his ex!! She calls him constantly! Everytime we've seen each other she has called. I told him it was really starting to bother me because she doesn't want anything, just wants to talk. He usually doesn't talk for long, probably because he tells her he's with me and can't talk so they hang up. She broke up with him and is now living with someone else. She's not telling her boyfriend that she's calling Jim and that bothers me because I think she wants to get back together with Jim. Jim says she didn't want him back until him and I started seeing each other. Jim says he will never go back with her but they were together for six years and have a lot of history togehter. They just broke up five months before Jim and I met so I should have known better to get involved with being the "rebound girl". I told Jim to decide what he wants, it's me or his friendship with her. I think they talk a lot more than what he's telling me and that's why she calls him everytime we are together. Why can't she just leave us alone so we can have a chance to be happy together? Appartently she's not happy with her current boyfriend otherwise why would she be calling Jim all the time. I'm about over this whole situation and don't think I'm over-reacting like Jim seems to think. I know he would be upset if some guy was texting me saying "can you talk?" while I was with him. I think I'm right by telling him it's her or me! I don't care how long they were together, why does he still want to be friends with her, she dumped him for someone else?