How can you tell if a girl hates you?

Try talking to her more often. Text her at least four times a day, and call her at least once. Follow her everywhere she goes at school, so she knows you care and won't give up on her. Also, take pictures of her, and especially any pets she has (without her knowing), then photoshop yourself into them, and put the pics in a envelope in her locker at school, or mail them to her home (the best way to go). When she sees you putting yourself into these photos, she will understand you want to be back in her life and things will be back to normal. Oh, and if she has any reaction other than what I describe, ignore it. She's just testing you, to see how much you want her.