Why is she being so horrible to me like this?

There is a girl who I work with, who I had a "flirtation" with about a year ago. I thought we were friends, then we went out in a group after work to a bar and she had a few drinks and was basically throwing herself at me. Although I like her as a friend I don't have those feelings for her so I didnt respond to her advances. After that there was a showdown between us. She acted like a total ***** to me and I called her rude in front of the team. Then we ignored each other for six months, before kind of making up, but before christmas she started being awful again. She constantly acts like she can't stand me when I have to go to her part of the office. She makes a big fuss of other guys in front of me. She refuses to cooperate with me. She snobbily ignores me. She won't even share the kitchen with me. Every time I have to ask her anything she acts like I'm wasting her time. I can't understand why she is still acting like this after so long. It is almost killing me.