Girl probssssssssssssss!!?

girl im seeing, act like couple together but she cant be "official" even though we are exclusive and do everything together. told me last week she is not over her ex and he has been calling her again as wants her back (he broke it off with her) 6 months ago and she told me that the only reason she is not going back to him is not because she does not want to but because im on the scene, so in a sense im holding her back. is it inevitable that she will and she is just dragging out the breaking up part with me? or should i just be a gentleman, mature and try to give her the best of me and show her all the good reasons why she is better off with me. really if she wanted to she could have just broke up with me and gone back to him but the fact that she is telling me all this and still hanging around must mean something worth fighting for? Thing is that she is acting so distant now as its like she is deensive as she knows she is messing me around, her way of making me wnat to leave?