It's happened to me more than once. She flirts with you, implies that she swings that way, and the moment you give in and start flirting back, she tells all her friends something like, "When is she gonna get the hint that I'm not like that!" without saying word one to you.
Or, try this one on for size. (different girl) She takes you aside before a party and pours her soul out to you that, although she doesn't know if she's bi or not, she's been sexually attracted to you since the day you met and she would like to try experimenting to see if there was anything to these feelings. So you go inside and go off alone with her. You take it slow and easy 'cause she's really nervous - just a little kissing and stuff.
Then she moves to California for a couple years with her new husband and when she comes back divorced she's telling all your friends behind your back that you make her uncomfortable.
I guess chick just don't dig me.