Is thsis wrong? - my friend...?

Yes! It sounds like even though your friend had you, she still needed to feel more accepted, so she started partying with her old group. It's not fair at all for her to do that to you since you were there for her in her times of need. You said that she said your friendship didn't work out because you didn't try hard enough, and that you're shy. She should have learned to accept the fact that you are shy. If you were used to her coming up to you, then she started partying, it's obviously her that didn't try hard enough. She didn't invite you to her birthday party after all you went through together? Wow. I'm not sure I would want to go to that party since she invited those backstabbers, though. I know where you're coming from. I don't think it says much about the kind of person your friend is if she's ditching you for people that hurt her like that. It sounds like she's not very loyal anymore. I'm so sorry all of this happened. I'm sure she's not your only friend, though. Go hang out with other people, and in time, Amy might regret all of the partying and ditching she did, and come back to you, and only then can you decide if you want to forgive her or take her back.