When you say "I do" are you meaning as you do at the current time or how you would if she were to be with you?

Anyways if you care about her enough, and your friends with the other guy, why not just move on. If you do care you'll have enough respect and enough sense to not get involved and be left on high toes and the only thing you can say is "I'll leave with my dignity" or something. Get off the high toes and move on.
And for not wanting her to get hurt. Talk to her and tell her that you think he's changed and your only bringing it up because you have your best interest in her or something like that. Tell her you just don't want her to wind up getting hurt. And if your feeling confident enough tell her something like...

I don't want you to wind up getting hurt. Your better off with someone more like me.

But don't go getting that noble thing on and get offended.

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If you and I were squirrels, could I bust a nut in your hole?
Love is a sensation, caused by a temptation, to feel penetration. a guy sticks his location in a girl's destination, to increase the population for the next generation, did you get my explanation, or do you need a demonstration?
You're good at math right? Is 69 a perfect square?