I have found one further candidate to be my great-great grandmother:-

Eliza Cowley was born 28.5.1820 in Ballaugh, to Thomas Cowley and Catharine Tear, who married in Ballaugh in 1806. Thomas may have been born in 1779.

If you are researching this family and they moved to Andreas after 28.5.1820, please let me know.
Thanks for your help. Janet - Email address should read jmitch2725@aol.com!