Both of you need to get std testing if you have had multiple partners.

It seems that she believes that sex gives her attention she would otherwise not get. She may equate sex to male attention/friendship. If you feel uncomfortable then break up because its still early yet and there is no huge commitment. Try to figure out what you want from this relationship and ask her what her expectations are. You may find that she is serious or that the nature of the relationship is a fling. Good luck!