Shillington PR transcript has marriage on 8th Aug 1812 of John Penn? of Baldock, Herts to Mary Shaw by licence. The licence transcript dated 7 Aug 1812 shows the same, both John & Mary being aged 21+ & surety given by John Flint, draper of Shillington.
There's a baptism of Mary daughter of Aaron & Sarah Shaw of 17 Oct 1784 (so where did 1791 come from?). Previous to that there's baptism on 14 Feb 1773 of Aaron, son of Moses & Susan Shaw, traveller.
Burials on 19 Sept 1789 of Sarah Shaw & on 3 Feb 1797 of Aaron Shaw.
So daughter Mary is orphaned at age 13 so maybe the Flints took her in, perhaps related?