Kudos to you for not getting yourself involved. You're better than that. She gets to enjoy both of you while you only get half of her. Go find yourself someone who will be totally yours instead of someone who's playing with your feelings.

Maybe she fell in love with you but needs time to take this serious step of breaking it off with her current partner. Maybe you just need to show her your love and commitment to reassure her that she should be with you rather than with him. People break up with their significant others, people get divorced, people change their lives. But she is risking a lot so you need to show her that you love her and are serious about her.

What if both risk a lot? Hard to take a first step when you don't trust each other. Worst case isn't rejection, it's the ruining of their current relationship with nothing better coming.

Not sure that's a good way to approach a new relationship guuuuys...

Yes, ruining their current relationship is a huge factor here. But there must be something missing in their relationship if she developed feelings for you. If you think that you and her have a shot, if you care so much that you are willing to take this risk, you should go for it. But take it slow - it is hard to take the first step if you don't trust each other. This is why first you need to develop this trust. You can take it slow while she is still in her relationship to determine if you both want to move forward.

this boat be still floatin' but taking on water. i'd much rather be boarding and plundering the one with the bigger sails!

Trying to build up courage, but terrified. Because of a past contacting her at all will end my current relationship, and I have no idea if what I read here is even for me. I don't even know how it could work out; it's so complicated now and not at all what I thought I would be willing to get myself into. I want what the OP wants. Please love me and show me, or don't show me at all! If I ran into her on the street I could tell I think, but as it won't happen, I need a sign.

@OP: I was in your shoes. Trust me when I say, cutting all your ties is for the best. You don't want this individual in your life, they will be stepping out behind you next.