I don't mean to scare you, but it is a complicated situation not impossible though. Everything is possible in the US as long as you have a good lawyer and a good luck. With that said, my friend, if you just apply to reinstate your fiance's Visa status without the preparation, chances are she may have to go back to her home country until her Visa get's granted. And yet,  there is no guaranty that whether it will get granted or not.

Easiest way to get a green card in this situation is, marry an US citizen...lawyer once told me...you know what to do next.

Good luck.