Sounds like Nicole has problems of her own and is spending too much time worrying about what other people are doing. When you were not with her, you did not owe her anything and after you are with her, what you said or did when you were not with her is not germane to her. That she had problems with relationships previously is not your problem; all you can do is keep telling her that it is not what is happening now, with her. But you can't "fix" Nicole for her, only she can do that.