After spending most of the day digging deep into all the Deming, Moody and Wethersfield info that I could find, I found nothing more concrete to prove that Samuel Moody's wife Sarah was a daughter of John Deming the immigrant beyond what we already knew, John's will.
I did manage to uncover quite a lot more about John Deming based on Vol 1 of "History of Ancient Wethersfield" along with coming across the reason why it was his daughter Hannah who married John Beckley as opposed to an "Unknown" daughter, all documented on appropriate profiles. The main problem is that christening and marriage records of Wethersfield (Deming) and Waterford (Moody) just don't go back that far. John Deming was on a list of Wethersfield church members in 1640 and in 1658 and appeared in town/land records during that time, so it's a virtual certainty that his children were all born there. Samuel Moody's father died in neighboring Waterford in 1655 and the marriage is estimated about 1658/59, so very likely one place or the other but the records are lacking.
All John Deming's other daughters are accounted for as married to other men who were alive in June 1690 when he wrote his will. But with the lack of records, could his "daughter Moody" been married to a different Moody entirely who vanished into the sunset? Maybe. I know this isn't much of an answer.