I work extensively with The Book of Dow, and checked it pretty thoroughly for any candidates for Rachel. There is a Rachel b.bef 1755 - in records of Epping NH Second Church as bap. 25 Dec 1755 with Noah and Josiah. There is no further record of her.
Another Rachel was b. 14 Dec 1754 in Plaistow, NH. Nothing more is given on her, but she had siblings who lived in ME. According to the book, ME did not keep vital records in Colonial days - so tracing people there is difficult.
Others named Rachel were either from wrong time period or married others. Sorry I can't be more help.