So it sounds to me that you have already chosen to support her. That can be a pretty hard thing to do, but completely possible. I know because I've already been though almost the exact same scenario.
I knew I cared for her, and only wanted her to be happy, so I let her do her own thing, while i still played the role of her best friend. I wish I could say the story ended with us being together, but though watching and observing their relationship i realized that she had some quirks about her that didn't sync with me. I knew then that I was happier being her friend than I would have been being her boyfriend.
So what I'm saying is sometimes you can learn more about a person when your on the outside looking into the relationship. take it as an opportunity to learn, and if the time come around again that she is single, you can make a decision then if you want to take another shot.
on a less serious note.
>>2 Air Force? :3