Hi ILovAnime,
I am so sorry to read your story -you are not overreacting. Bullying is a very serious problem which affects millions of children (and adults) throughout the world. So you are not alone! It is often a problem which goes unrecognized, even when the person being bullied draws attention to it - as you have done. Your parents' apparent lack of support could possibly be because your parents may be so horrified at the thought of you being bullied, that they may refuse to believe that it is happening.
Maybe, could you ask your Mom to secretly listen in to your study sessions? In this way, your Mom may be able to overhear some of the things your friend is saying.
There is a possibility that your friend is acting like this because not all is well with her life and she is piling all of her anger on to you.
Please keep strong, there are so many people on Christianity Oasis who can offer you support and better advice than I can offer, but keep your trust in God and He will see you through this so that you can be stronger - you may even, in time to come, be able to help others with similar problems because you have experienced this.
Keep strong!!!