My friends are starting to ignore me. What should I do? I've been really sad lately?

The main thing you need to remember is that no one can control your friends. If you are feeling sad about it, tell your friends that. Come to them honestly and candidly and tell them you don't know what to do. Tell them everything when the other girl is not around---that is necessary, just in case it turns out she is responsible. As you talk, monitor your friends' reactions. If they act like they don't know what you're talking about and seem to be completely open, they may really have no idea. Otherwise, if they seem nervous (like they are lying), you really need to let them know without saying that if what they're doing continues your trust will start to fade with them. The fact that they're ignoring you points to the suggestion they're very immature, so make sure to be completely serious about it when you go up to them. If they laugh it off and continue to ignore you, there's also the choice of getting to know other students who your friends like but you don't consider friends and asking them what's the matter. Sounds sneaky, but I've done it and normally a friend's friend will tell you the truth (though be careful because they might bend it a little). Just in case you are not happy with the length of the answer, sorry about it, but I don't think you'll mind as long as I have given you the right advice. I sure hope I have. :-)