Well I got your PM first and then I read this, so just ignore the PM.
Ok. I know how you feel. You don't want to just talk to her in school because she will think you are some weird creepy kid. Now i don't necessarily agree with taking the "myspace route", it seems like it would be easiest for you to do. But i don't think you should do it. Here is how i see it, and she might see it the same way. I am not sure if she added you as a friend or vice versa but she might find it kind of weird or odd that you are just messaging her now. Most girls will realize that you like her because you are messaging her on myspace when you normally don't talk to her. then she might ignore you all together.
you sort of gave a lack of info because I have No idea how old you are, what grade your in, is she in any of your classes, does she even know you exist, have you ever talked to her before.
Now i am guessing that she is in your class or maybe she isn't. But anyways, I know it sounds like a million times easier to talk to someone when its over the internet, but this could be a turn off to her, and it could bring down your self confidence. I never talk to people over the internet unless I have spoken to them at least once or twice. Now unless your school is really small or she is not in any of your classes, i suggest you talk to her.
This isn't only dealing with relationships, but social dynamics as a whole. If you can't talk to her when her friends are around, how are you going to act when its just the two of you. I know how you feel. You want to catch her when she is alone, when it is just her standing by her locker or whatever. But like you mentioned, she is popular and she probably won't ever be alone, unless its during class and she leaves for the restroom or something like that.
Now i talk about this a lot, you might not know since you are new. Confidence is everything. when you walk, talk, eat, do whatever you are doing, you give off a vibe. It can be a positive vibe or a negative vibe, but there is definitely a vibe. the vibe you give off depends on the way you are acting, communicating, handling situations, and presenting yourself. Just make sure that you are giving off a positive vibe because she will definitely be able to tell.
Confidence, confidence, and more Confidence. If you don't have any you won't go anywhere in life. If you aren't confident in yourself, how do you expect your crush to be confident in you. the way you handle and present yourself can set the tone for the rest of the conversation.
If you could just answer these questions i could help you a ton more
you sort of gave a lack of info because I have No idea how old you are, what grade your in, is she in any of your classes, does she even know you exist, have you ever talked to her before.