I am jeaous of this girl (she's not prettier than me)
I don't understand how she can be so mean and have this really sweet
Very good looking guy.*they just started dating so I don't think he knows her well*
The thing is she's always competing with me.
I just want to not care. Even learn to treat her like anyone else.

She's probably competing with you because she feels like she has to. She might even be jealous of you, who knows. You two are very different, unique people. Don't try to be like her, don't even be around her or speak to her if she annoys you that much. It's not her fault that she's got a good boyfriend. It's your fault for caring, and it makes you the jealous loser. So try to pick yourself up, because if you want to be better than her, then the first step is to quit with the jealousy.