I believe it would have been impossible for Sarah to have been the daughter of Joseph and Ann Robertson Bays if she was born about 1745.Joseph was born about 1730 and married Ann Robertson in Halifax County March 22, 1757. John Robertson, surety. William Wright Witness.
I suspect that it is more likely that Sarah was a daughter of Peter II and Sarah Unknown Bays. The Usserys and Bays families were long time neighbors in Henrico and Goochland Counties.