She's taken, I believe we're meant for each other.

Tell her.. either by person, phone, or email/letter.. you've got one life, live it!

Tell her your feelings. She'll either reject or accept you, and your personal suffering will be over--there will be no more "what ifs."

I think you should tell her. Kinda. I would advise against it, except you're obviously hurting, and this isn't something you just want to move on from. I'd tell her, but make it clear (whether you mean it or not, this is important) that she shouldn't feel pressured to leave. She should leave of her own free will, and taking the pain of love isn't easy, but it's possible. Don't worry, and also, don't send her an email. It feels pretty impersonal, talking in person would be the best.

I don't know here. She has a boyfriend, but talks to you? Well, I guess you have to decide if she is just trying to be your friend, or if she is having problems and is thinking about you as a boyfriend replacement. Until she officially breaks up with him, its going to be hard for you to establish a relationship with her. Its obvious you are head-over-heels for her, but she may not feel that way for you (yet). Just continue to talk and be friends until she loses the boyfriend. Then you can tell her how you really feel about her, and pursue her!