What did she do that you perceived as flirting? It would help to know what she actually did. Is it possible that you thought she was flirting when she was only trying to be friendly? Often, a kiss on the cheek is a friendly gesture, not a romantic one. Did she do anything overtly romantic/flirtatious? Of course, it is also possible that she is in the closet or confused about her sexuality, and you brought that out in her. But, if she is straight, maybe there was a misinterpretation?