Here's my rule for loaning money to friends or family and it's supported by Dave Ramsey, a well-known financial "expert."
If you give money to someone, consider it a gift. Very few people will actually pay you back, so consider that fact and if you think the relationship is strong enough to withstand the possibility of not getting your money back, then loan it. Otherwise, say no.
My brother and I have "exchanged" money when we've had it - but never expect it back. It keeps the arguments under control.
Don't loan money you need back. Just don't. If you get it back, it's a plus, if you don't - well you didn't expect it anyway.
She probably is feeling guilty, or perhaps she was using you for that money, one never knows for sure.
I hope you clear up the trouble. If you like her a lot, tell her to forget paying you back, see if she warms up to you. If not, you'll have your answer, which is more valuable to your future than the money!! =))
Life lessons, yes?