How about I keep my friend around just to bully her?
That's messed up. Why would you want to be so mean to her?
It makes me feel better about myself.
It's really bad to keep someone around just to bully. It ruins their life. You should either be nice to your friends or find new ones.
I don't think that is ever logical.
You are smart enough to know that bullying is not cool, and how are you a friend if you are bullying her? I think you should stop bullying her because other people will see and find out and might try to bully you back just to make a point. There are a lot of other ways to feel better about yourself, and I think you should look into taking boxing classes or doing mixed martial arts.