@Peebles1,
Leave her, this instant - send her an email telling her that you don't that sort of behaviour, and consequently her, in your life. Don't answer her phone calls.
She wants you as her fall back option (ie if she doesn't find someone she really likes, she will 'settle' for you, so that she is not lonely). It's an incredibly disrespectful thing to suggest.
If you let her walk over you like this, she will have no respect for you (why respect you if you don't respect yourself. Why respect you if you put up with bad behaviour and let yourself be trampled over?)
edit : in respect to the email - I would suggest this method because it allows you to set your thoughts, and not have her argue with you. If you allow her to argue, she will seek a way to blame you for her behaviour. Normally a breakup deserves a face to face, but not this sort of behaviour.