I can see where both sides are coming from. At first I read this because of in spite of the bullying. (I might be an angst junkie when certain moods strike me.)
But as each chapter goes on, it's becoming more clear that it's not so much bullying as the childish "teasing a girl you like". Except that she should have grown out of it by now. And she doesn't seem to care whether others see her as a bully (or possibly wants them to, to keep her girlfriend to herself). Then combine that with what even appears to be some unintentional bad timing, and even some help in bullying from the girl being bullied... It's like a perfect storm.
And they both seem to like how things are enough not to mess with it.