Why did she slap me across the face?

My buddy and I talk crap about her a lot because it's funny. I stare at her all the time. She always catches me staring at her. We gave her this candy bar thing to make her gain weight, gave her foot cream instead of face wash. We had one of our female friends make out with her boyfriend. We made her cry once, it was funny. I guess she had enough yesterday, because she came up to me and was like, "What is your problem? Leave me the hell alone, I haven't done anything to you!" Then I told her to chill, and then I grabbed her and kissed her then she slapped me across the face. Then a couple days ago I went to where she worked, and she saw me and went to the back. Why? What's her problem?