A contrarian perspective: I was in the same position as your fiancee.

I was in over 20K in consumer debt. At a particularly low point, after finishing grad school, it was closer my annual income (working $15/hour, 35 hours) than I'd like to admit.

Was still quite in debt when I met my fiancee, who is the most responsible person you could imagine. He is actually a lot like you, extremely frugal. Such a good saver that he was able to secure a 20% down payment for an urban duplex, right out of college! You could scour his credit card statements (which he uses to pay off all his bills) and count the number of charges on one hand for months, and never see anything more discretionary than the occasional fast food meal. That's how frugal he is.

His example, and that of his in-laws, quite frankly, shamed me even more than I was already shamed. I got off my collective ass and changed myself. Then when the cashflow started reversing from negative, to positive, I joined Fool.com to know what the heck to do with it and started researching investing like crazy.

I finished off the consumer debt before our engagement. We've been happily married since last year. He was initially horrified to learn of my consumer debt and greatly worried, but my attitude and habits have done such a 180 that he now trusts me to be in charge of our money and investments (though he's frugal, he hates anything else to do with his money for some reason--his father was still doing his taxes, for example). We save well over 50% of our income--gross, not net. All our accounts are joint except for his mortgage, which existed before the marriage. He even put me on his credit card.

I still have 10K in student loans but at a 2.12% fixed rate, it just doesn't make sense to pay them off. Plus I can now pay them off, quite a few times over even, if such ever struck my fancy.

If I'm salvageable, she may be. Do talk to her, and insist on having her address her debt before marrying her.