Sorry, have changed emails so didn't get the notice re this message.
Unfortunately this Harriet is not yours. She was born in 1820 and died in 1821. Have you tried looking your Harriet up in the 1841 and 1851 censuses? At least Scrimshaw is not a terribly common name. I wanted to have a look for you know myself but ancestry.com is down!
Good luck with your research, sorry I couldn't be of more help.