...I have reason to believe that her current husband cannot own firearms. I remembered that he sees a parole officer and some other issues.
My opinion:
So you have no actual proof that he cannot own a firearm? Might wanna check this out if you can before you make a decision. What "other issues" would make you not want to fulfill your word?
I am no lawyer but if they sold them to you "paperlessly" and you sold them back to her "paperlessly" then would there be any proof that you actually ever owned the guns? At least any that would prompt a prosecutor to bring charges? I can't see how selling a gun to someone who can legally own a gun is a problem, especially when you don't know for sure whether her new husband is a felon or not. Is seeing a parole officer a definite indication of him being a felon?
I agree that going through an FFL is the "safest" way to go and it's your posterior at risk, not mine. But it rubs me the wrong way. And I disagree with previous comments, if you do to through an FFL YOU should pay any and all fees since it is your requirement to fulfill your word.
Sounds like there is a little more to this than it appears?