Which one?

[Michael]

John Norman married Sarah Warren in Tiverton, Devon, 24th July 1814. They had eight children, all baptised in Tiverton - Robert (1816), George Henry (1820), John (1822, d1824), John James (1825), Georgiana (1826), Ellen (1829), Emma (1832) and Frederick (1835).

There were two people named Sarah Warren baptised in Tiverton in 1792 - one on 22nd April, the daughter of Thomas and Mary Warren; the other on 12th July, the daughter of Isaac and Sarah Warren. There are several Ancestry trees which include the family, and all of them show the Sarah who married John Norman as being the daughter of Isaac and Sarah. I can't see what evidence there is that she is definitely that one, rather than the other baptised the same year (and I know better than to trust an Ancestry tree unquestioningly!) - can anyone help please?

I had hoped perhaps one or both parents might have been witnesses to their marriage, which would help - but unfortunately not. One of the witnesses was a regular (also witnessed another marriage on the same page of the register), and the one unique to them was William Sheppard.

There is also a Sarah Warren marrying John Frost in Tiverton on 17th March 1821, which is probably whichever of the two born in 1792 hadn't already married John Norman - but the witnesses' names that time (William Perram and David Reeve) don't help either.