Why would you want to play second fiddle? She has a boyfriend and you are her bit on the side - she has cheated on her boyfriend before and has no remorse whatsoever as she is willing to do it all over again. She sounds rather selfish and greedy. You should definitely refuse the little she has to offer, find yourself a girl who is ready and able to give you what you want and deserve, there are plenty of those out there!
[SIGPIC][/SIGPIC]
Love is like a merry-go-round: you get all dizzy, and then you feel sick!