Excuse me for a second; IF it is shown as income, then no crime was done.
IF she later claims she earned it with favors or other off the record activity, the money trail would only reinforce her phony claims. So, the thousands and thousands of dollars have to be accounted for some how. Any mistake made now will bite that person in the ass later.
As I recall, it may be possible to demand the bank refund any checks forged and cashed that are less than 1 year old. I am not going to lay out my experience with this, but the first step is to be realistic about the potential to get the money back. This chic won't have any money, not ever, unless she hoards it in the bank. Not likely.
So you let legal action do the talking, criminal, not civil. Depending on your location, the powers that be may not be interested in pressing the charges, if in their opinion the amount is not large. Tough shit, press the issue, make it happen.
Then you can get damages either via criminal court or through civil action. She may never be able to pay it back, but I think she will never get a tax refund as long as she owes the money, your boss will get it, and she will go to her grave paying on the judgment. Bankruptcy does not clear legal judgments either.
Even at $200 an hour, 30 to 60 minutes now with the atttorney pays for itslef by having a plan now. He or she may say screw this, walk away from it, end of story. Typical of the con artist, even after she is caught, people buy into her shit and fail to take action. That is how she got their trust to begin with, she is THAT GOOD!
PS is she hot and single?