Fuck it, you're barely communicating with her as it is and you're stringing along your pain. Tell her about your journey, tell her you've realised what you actually want. Preempt it with understanding that she may not want to maintain contact and that her fiancé isn't comfortable with you being friends. Tell her you're sorry and exactly how you feel, then drop the bomb.

Like you say, two possible outcomes most likely - either you nail it and she feels the same which is a win for you, or she accepts/appreciates it but is happy with the other dude and you part ways. You'll feel better for finally telling her and if it doesn't work out, you can move on without being reminded about her all the time.

This is a selfish way to do things but at this point can you really see you staying friends considering her fiancé is already uncomfortable with you being in contact with her?