I'm not Oprah, or Humphrey Bogart....but something in this story isn't adding up.
You're best friends....but you can't be friends because she's with another dude?
That either means you told her and she went another way or it creaped her out...the other dude can see it in you and doesn't want you around...or you're really butthurt that she got with someone else.
It sounds like you missed your boat....time to move on.
Life is a river, not a puddle. You can't swim back up shit creek with a baby spoon.
Other than having intercourse with another man...this outpouring of emotion might be your gayest moment.