What was that all about? please help?

Ok, so today in the library me and my crush were there and she was shelving books with some kid and all of a sudden she comes over to me and was like "by the way, my sister DOES NOT like you' because the other night i told a buddy of mine that she did. and I was just like ok whatever. then she called me back again with her friend there and she said "Paul has something to tell you" and he told me basically how obvious I was about liking her and she just grinned and I panicked so I just said well that's not true and she came over to me and was like "wait, you don't like me more than a friend?" and then she was upset and fake crying and that kind of stuff. My question is, I've known this girl for about a year now and we've always been friends except we went on a date once. Could she really be that obvious that she wanted me to think more, or is it something else.