Hello again Louise,
I'm still looking!
Think I've found her on the 1861 census, but transcribed as Louise Moyce.
RG09/75 Folio 129, page 6
Marylebone, London.
She's living with a Margaret Evans, Dressmaker,
Mary Ann Worthing, also a dressmaker,
then Louisa E Moyce Unmarried 18 dressmaker, born Harwich, Essex.
I can understand the difficulty - there are so many ways the surname Moyse could have been spelt!
Yorkslass