Yes I definitely recommend therapy if you have the time and money to afford it. Its always good to open up to someone else to help you get through it all. Im so sorry for the way those girls treated you. Some people take a sick pleasure in hurting other people for their own benefit. But sometimes because theyre just so messed up themselves.
Im a teenage girl, and although i wasnt bullied by another girl there were some girls I knew who were total b*tches. This one girl especially... who basically used me and then took my only friend i really cared about away from me. *sigh* I still wish i had done more about it to make things okay again. But well not all girls will bite you in the back, you just have to do a little searching (and trusting) to find them, but they're out there.