I can understand how desperate you must feel and possibly home schooling looks appealing as an option but the one option you don't seem to be exploring is how to teach her to stand up for herself. In life, at work and socially she can't just opt out when things get tough. No-one has the right to hurt someone else and of course the school need to act to stop the bullying but you also need to teach her some basic anti bullying strategies.
1) Tell her to start noticing girls who don't get bullied. How do they hold themselves, what do they do and who do they talk to? By emulating their behaviour, especially the body language she will communicate a 'don't mess with me' message.
2) What are her beliefs? Does she have low self-esteem? Does she believe she deserves to get bullied? No-one deserves to be bullied, when you change your belief you change your external expression of the belief.
3) It's easy to notice what isn't working and focus on the bullying which is the problem but she isn't bullied 24/7 so get her to notice good days, what happens when she isn't bullied? She needs to focus on positive self-belief and self-worth, believe that she has the right to be safe at school and that it is they not her who is in the wrong.