I don't have Sarah. But if she died in 1835 at age 37 she would have been born about 1798 or 1797. In 1790 my ancestor Pelatiah lived in the Portland area.Portland was part of Falmouth which broke up into towns Cape Elizabeth, Westbrook etc.
My ancestor Pelatiah Fernald and wife Abigail Strout lived in the Portland area in 1790. He's the only Fernald listed. They had four sons and possibly 3 daughters with only Mary listed in genealogies. Pelatiahs daughters would probably be too old for your Sarah. His son Nathaniel moved by 1790 to Vinalhaven and his children are well documented. Joseph married Mercy or Mary Lake in 1800 so you can exclude him also. Anthony stayed in the Portland area and married four times. He was married to Elizabeth Butler in 1794. She died in 1800 and only their daughter Eunice is listed in genealogies, but I would check the 1800 census of Portland to see how many females he has listed 5 and under. Look for Anthy Furnald. and Joshua married Mary Gooding in 1796 in Portland. But no children are listed in genealogies I have seen. Again I would search in the 1800 census to see how many children he had living with him. Check for any other Fernalds in the Portland area up to 1820 and that should narrow your search.