I have a Sarah Fiske who was reportedly born in Waltham on May 14th, 1718. Her parents were Lt. John Fiske and Mary Whitney of Watertown, Waltham and Worcester. I don't have Sarah dying young or marrying at all. But I don't know when she died either so basically I don't know what happened to her. But at least this Sarah is worth looking into. Her father John died in 1758 and is buried in the Old Burial Ground On the Common, in Worcester, Massachusetts. Her mother Mary was supposedly buried in Waltham in Feb. of 1725. A sister Abigail married a man named Stephen Sawin and her sister Mary married a man named Samuel Hagar. She also had a brother John who married an Azuba Moore.
None of the other Sarahs in my data base fit. Good luck, Bob Birt