For as long as I've known her, this girl has been very quiet around new people but she is fine with the group she's in including myself. We are quite close but sometimes she drives me MAD :mad:!
She's been doing this a lot since I've been around her (we're quite close friends) saying really inappropriate phrases which are racist and very very rude, and she does this in public. She is also very anti-sociable and hardly speaks to anyone but me in my classes (which I find really clingy). She never ever speaks to anyone in classes we have together but just to me. And its really affecting my sociability in school too, because I am constantly around her, and never have the chance to speak to different people.
I mean no offense to anyone, but I really think she has psychological problems as she has very strange behavioural issues.

I would go on with the many other problems she has but it would take ages :( please help!

Since she is a friend and not a girlfriend try spending less time around her. Tell her you have things to do. Spend time with her in the group mostly.
Also when she says inappropriate racial type things interrupt her with ''You know in some places you can get really messed up for saying stuff like that."

It sounds like in a way she may be a bit shy. Since she's known you for a long time she's probably comfortable around you and therefore feels she can make certain comments around you. The next time the two of you are alone try talking to her about your feelings. Tell her you don't like it when she makes certain types of comments and that you don't agree with her point of view.

One thing you can do for yourself to meet new friends is to join some school activities or clubs without her. School is a great time to expand your horizons and to try new things so take the opportunity to break into your own personality and hopefully she will do the same once she sees that you're getting your own life.

Start distancing yourself from her. Make plans with other people.

When she makes racist comments, tell her that it makes you uncomfortable. If other people see that you tolerate her racist attitude, you may get labeled as a racist also.

One good way to get her off your back (and help her out as any good friend would) would be to find someone that you think she may like, and introduce them.
That way, you can help her make new friends, and help yourself, getting some quality time without her.

As far as the racist comments go, just tell her that you don't appreciate them. If you have problems with the way she jokes, that it is uncalled for and immature. Tell her that there is no reason to say anything bad about any other people, and if she can't accept that, that she should go away when she needs to say something like that.