The number on the 1841 census is clearly 35 not 25. Ages in this census were rounded down to the next 5 years, so her age could be anything in the range 35-39.
If you use the GRO online index, rather than familySearch, it gives her age – 36, registered in the Oct-Dec quarter.
Her burial must therefore be the one at Watton at Stone on 24 December 1841, age 36:
https://www.findmypast.co.uk/transcript?id=GBPRS%2FD%2F72214208%2F1
Her date of birth is therefore implied to be slightly earlier than you have it, 1804-1805.
However, the marriage record has the 'with consent of' struck through, implying that the minister thought both bride and groom were over 21. If he was right, then she was born by 1802. This is not far off 1804, and the sort of variation that often occurs.
As well as the baptism at Cottered in 1798, there is one there in 1801 and also one at Standon which is a bit closer to Watton.