There's this girl in my class who steals my friend, and what should I do to get my friend back? I'm so lonely now and I just want revenge.?

Well, you can either prove both of them right or wrong. As far as I can see, you're about to turn into what Dumb is trying to describe you as. Is that what you really want? In other words, keep your cool. Don't let them sour you up or make you become salty. Is Brainwashed really worth fighting for if she is easily giving up on you? There are better people out there. Why waste your time on these two if they're already bringing out the worst in you??? Some friends. Keep respecting people even if they don't always deserve it. In the end, you'll be happier than they ever wish they could be. Happy people don't go around making others feel useless. In time I am certain they will backstab each other and will not remain friends for long. Life will teach them. Now onto you. The first step to letting go of your best friend will suck but at least she won't be holding you back once an even better best friend comes along. Believe in yourself, be kind, be interesting and people will flock to you.