Gosh, young teenage girls can be so petty at times. I've been there and done that myself. I'm glad to say I wasn't the person who started the drama, and from your story, it seems like you're in the same position that I was in, or a somewhat similar one. Really, all I can say is that things will get better. It seems tough and unbearable right now but, these people are not good for you and it's not possible for you to maintain a healthy friendship with them. They're being too childish and immature for their own good, it's not worth your time. Even if you go back to them, they're still going to give you grief in one way or another, so do not bother with them anymore. If it were a small falling out, I'd say there's a chance you could apologise and sort things out, but it clearly isn't.
Please, just go out and make new friends. You said about that Amy girl who was nice, why don't you talk to her more if possible, or just anyone you sit next to in classes who you quite like. Just ask them politely if you can hang out at lunch, and don't let it terrify you. The chances are they will say yes, and what's the worst that can happen? They could say no, and that's that, and I doubt they'd even say no. I don't want you to do what I did and settle for friends who make you feel like crap all of the time. It's horrible. School is hard as it is, and we already go through a significant amount of stress as it is, so you don't need to add to it with petty friendship problems that your so-called friends are causing.
When you leave school, you will realise quickly how insignificant those people are to you. You will probably not keep in contact with them and you will be glad that you didn't, because whilst the majority of some people grow up, some people just remain nasty. You'll find it much easier to make friends. Sure there are still some petty arguments that happen, but it's really not over something so ridiculous. I mean I'm in sixth form, and I can say I'm glad that I am no longer in year 10 or 11 again. People are so immature, you don't realise how much you grow up. You seem like a really mature and grown up person who doesn't tolerate rubbish from friends and doesn't cause drama, so I am sure you will be able to befriend other people like you, and I'm sure you'll be able to get through this and make the right decisions.
Good luck, and if you need any more help, feel free to PM me.