You are letting her use you, dumbass. Whenever your girlfriend starts to waver don't interfere. If she likes someone else, there is little you can do to make her like you, and even if you get her back she will likely do it again. Tell her to make a choice, and leave it up to her to stay or to go. If she stays good, if she goes then NEVER, EVER talk to her again at least for the next few months or even next few years. After a while though it may be nice just to talk to her again and catch up on her life, remember the memories and the such. However, never dwell in the past. You made a big mistake telling her that you still love her. It just encourages her to do shit like this and it makes you weaker.