Why does my girlfriend want to end our relationship to be PROMISCUOUS?

I've been seeing this girl for a little while and things are great. We are both really into each other and the is great. The only thing is she keeps telling me she gets bored easy and that she wants me to know now that she will be breaking up with be to have with other guys in the near future. She says she doesn't want me to be hurt. This girl is a great girl and there is obviously some underlying issue here. I don't think the issue is between her and I. I believe it has to do with her past relationships with guys who have treated her like garbage and she is insecure with herself. This girl means a lot to me and I would like be able to help her out.