... in order to get them to agree it's invalid and drop their arbitration proceedings. Offers in lieu of judgment aren't uncommon.
It's most likely she'd have to give it back if a court declares the NDA invalid, anyway, or would at least make her case that it was never valid more solid if she's not trying to keep both the money and speak.
There's several ways the contract could be considered invalid now. First, that it was never valid because it wasn't signed. Second, because Trump's attorney spoke of it, he broke the terms. Third, which I'm not seeing argued yet but she should consider, that Stormy learned after the fact that the contract and the way the Cohen/Trump handled the money without reporting it constituted a violation of election finance laws, and she doesn't want to be part of an illegal contract (illegal contracts are always void).
Usually people will start with grounds to establish the contract was never fully entered into (the not signed part), then go with "in the alternative" arguments.
For example, a friend was sued by a debt collector who didn't obey state law by attaching either the cardmember agreement or an affidavit stating it was unavailable. His attorney filed a motion to dismiss based on insufficient process, a motion for a more definite statement (giving them 10 days to amend to add the cardmember agreement if the judge decided not to dismiss), and a generic answer in case the judge rejected both motions. Potentially overkill, except that they bit on responding to both Motions and admitted the documents had been available but requested more than the 10 days because it was in another office. His attorney said their response admitting they could have gotten the documents before filing meant the process was officially insufficient. And thus got the dismissal, even if the evidence for the dismissal came in their response to the MDS motion.