What's the best way to ask her to prom?

If she's a good friend then you should ask her I mean she isn't going to feel awkward she'll be flattered! And it's better that you guys are friends rather than some random guy asking her. Just make sure she doesn't have a prom date already.

So are you two just in the friend zone? Do you want to date her and how would she feel about going out with you? If you two have always been friends and she treats you like a friend, then I don't think she would like that idea. Some people go to prom with their
friends because they don't like to be "look down" by others because they didn't go to the prom. I think prom should be between two people who like each other instead of going there so you are a part of something. Have confidence my brother. A guy with confidence is invincible and also charming to the girls.

Since you know this girl for so long, why are you so nervous to ask her to the prom?
1. Make sure she is not going with someone else already before you ask her
2. What are the chances you think that she will go with you
3. If there is a pretty high chance, then just ask her and be confident
4. Don't think too much and just be casual
5. Why do you care about her thinking that you are desperate?
6. Don't worry about getting hurt. Someone should advance so we can end this stalemate.
7. Be casual, be confident and don't be a pussy, just do it.

Whatever... just say it plainly and calmly. Then she'll think that you like her and then SHE will have to decide what to do next but at least your feelings are known.