Perhaps this couple checked around and found that the H&R or the other big chain preparers would charge them a higher fee to prepare their returns than they've already paid to you, and now the wife is trying to get a return from you to file. They've probably already done that, received the same result as your return showed, and they, or the wife, have again demanded their documents back and refused to pay, this time under the pretense of the return being wrong.
I think you could ingor the whole thing and be done with it.
Or you could attach Form 8948 and also get the signed statement from them that they've requested you not file the returns electronically and give them a completed package. If you do give them a complete package, be sure to attach any W-2s and 1099s showing withholding, and any other required attachments. You might tell the wife that there will be some nominal charge for printing, assembly and signing the return since those functions were not included in the amount they already paid to you.
I would not simply give them a copy of the return if you go this route.