I don't think less of you B Deserter. Zeroday is speaking from his own pain. In actually, his life was not ruined or destroyed. What happened, saved him from a bad marrriage with a woman who never loved him. That woman getting falsely engaged to someone just to make someone else jealous was a shitty thing to do. He is better off and doesn't seem to know it! I think your situation is a little different.
I still don't think it is a good idea though, and here's why. If you are not a JW and she is, you will have nothing in common. Her beliefs are lifestyle are all-encompassing. Chances of it working out well: slim to none. It's not like marrying a lapsed Catholic or something.
Other reasons: you said she was engaged, but her fiance had not proposed. This is contradictory. How did she get engaged if he did not propose? If no one proposed, then she is not engaged. (I suppose she could have proposed!) Are you even clear what the situation really is here?
What does losing weight and martial arts have to with any of this? JW's are also against martial arts, you know. Or maybe you don't.
Finally, if a woman is interested in a man she gives him clues to let him know, so he does not have to needlessly go around making a fool of himself asking out women who are clearly not interested. Do you know what the signals are that women send out, and has she sent any of them your way?
Cog