I sometimes feel like randomly pulling this girl's hair.
That seems cruel. Why do you want to pull on her hair?
She's just naive and she also has terrible English.
Someone not having good English skills is not a reason to be mean to them. It is rude to pull the hair of another person, and there is no reason to do that to someone else.
It's fine. She deserves it because I don't like her, and I know I can get away with it.
Just because you can get away with it doesn't mean you should do it. It doesn't sound like this girl has done anything to you to give you a reason to be mean to her. I think you should try to be nicer to her and just more considerate of others in general.