Please help!

[schizaea]

OK, so for the last 2 years my friend has liked a guy who is a total douche, he was horrible, always trying to wind her up and making fun of her with his friends. Now luckily, he's moved schools, but she likes this other guy who is even worse.
He's in our year and he makes fun of her on fb and just in general gives her crap. Me and some others have all tried talking to her, because this guy gives her really bad self esteem, but she still insists that she likes him and that arguing is how they 'interact' or just 'get along'.
I'm kind of at the point where I don't really know what to do, she's just sad a lot of the time. I'm not sure if it's because the guy makes fun of her or because he doesn't like her.

How do I get her to see that he is not worth her time, and that there are tons of other guys who would love to go out with her and would make her feel better about herself?

[Mortal Coil]

This won't be easy.
Chances are she likes these douchebags because she has low self-esteem to begin with, and when they reinforce her feelings about herself she actually feels better because she was right about something.
try getting her into hobbies of her own. Go to gigs together, treat her to a day at a theme park (or a bar, if you prefer ;)), or get some of these "better guys" to play 2-on-2 basketball. Once she develops a more distinct personality of her own she might start to see sense. It will be tough going at first, but good luck!!!

[Triceratops]

Tell the girl to get a grip. What is the point in going for guys who will treat you like crap when there are some really nice guys out there. And girls moan why relationships never work out or why guys are dicks...

If someone doesn't like you, move on. Every single guy I've ever liked in my life has never liked me back. Not one of them. But one thing I do is never go back to them, I just forget about them instead.