Should I apologize to this girl?

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 put a dead fish inside her locker, and put worms onto her head at lunch. She was walking to her table at lunch and we got someone to trip her and she fell face first into her lunch! 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. Should I apologize to her? How?