Possible Sarah Spencers:

bp 1780 f:Frances Beverly, St. John
bp 1782 f:William, m:Mary Long Riston (Hull)
bp 1785 f:Edward, m:Mary Mastermann, Stillingfleet 43 miles east of Hull
bp 1788 f: Geprge, m:Sarah, Hull Holy Trinity

The 1788 Sarah can likely be ruled out as she would have been 11 at marriage.
The 1785 Sarah can likely be ruled out as she would have been 14 at marriage and distance from Hull is great.
The 1782 Sarah is possible as she would have been 17 at marriage and 20 at birth of dau. Dorothy and she was baptized in Hull, 11 miles south of the city in which dau. Dorothy was baptized, Beverley England.
The 1780 Sarah seems most likely. She would have been 19 at marriage and 22 at birth of dau. Dorothy. Moreover, she was baptized in the same town as dau. Dorothy, Beverley England. And quite possibly the two were baptized in the same church. 1780 Sarah in St. Johns. Dau. Dorothy in St. John and St. Martins.