I've been through what you've been through with an equally-in-need-of-counseling fiancee some years back and I think I was just as blind at the time that the girl had SERIOUS issues as you are to that fact with your ex. Why haven't you gone to your bishop yet? Seriously. If this is about "your mistakes" and "your burdens" go see your bishop. You keep saying you need to but are on here instead asking if you should go tell her bishop so that you can prevent HER wedding. The simple truth above all else is that you aren't, as you see it, carrying some sort of burden for whatever she did wrong if she does or doesn't repent. Your responsibility in terms of your repentance is to take care of yourself. If you repent and she doesn't -- that's not on you. As to whether you tell her bishop, be mature and let her move on and live her life. What she discusses with her bishop/stake president is between them and God and NOT YOU. If you feel she's not worthy, guess what, it's not your call. You don't get to decide that. If her bishop signs off on a recommend and she lied to him, that's between her and God. And not you. I get that you feel responsible because you were a participant but it's not your place to act as her bishop and decide her worthiness. Do people go through the temple unworthily? Do people take the sacrament unworthily? Sure. No question. But that doesn't mean that because they don't "get it" now that they won't figure it out down the road and repentance is still just as available to them then as it is now. A person can repent from both sins and from going through the temple unworthily. And if the person doesn't - well, that's between that person and God and, to be blunt, but who are you to make a judgment call on ANYONE other than yourself?? I get how much she probably broke your heart and how much you want to tell her bishop and for her fiance to really, really know (particularly by way of having the wedding pushed back or whatever) because I've been there and it hurts to feel wronged and like you're getting the short end of the stick. But if you really love her and you really want to be altruistic, leave it alone, worry about yourself, and let her work her life out on her own. She knows right from wrong and it is NOT YOUR PLACE to try to force her hand if she chooses something different than you want her to do. Let her live her life and worry about yours. When I was in your situation, as hard as it was, I left it alone, and now looking back it was the best decision in the world and I'm glad I spent a little more time worrying about myself than my ex. (as a sidenote, if you really think that if things between her fiance and her were to end that you at this point, without years of counseling for her, have a shot at a happy marriage with her you are myopic and unrealistic. You've written enough about her to indicate to anyone objective that she has a LOT of stuff to get through before she will be ready for a happy, functional marriage.)