Go ahead and downvote me, but this is so wrong on so many levels.

Everyone does mistakes at some point in their lives. It's human-like. OP cares much more about his finances rather than his fiancée. In this case, I pressume money come first. It's crystal clear to me those two meant to be if OP wants to call off the wedding over her past. Yeah, maybe she lied by hidding this matter to OP, but please, before making mean assumptions walk in her shoes. I'd say she was too ashamed of her past, so that's why she chose to hide this from him, which probably it's caused of lack of communication and trust on both parts.

I acknowledge that both of them did wrong. She deserves someone who will understand and accept her past and OP deserves someone like him. There's a saying in my mother tongue: "Those who are alike, gather together".