In Scotland the eldest daughter is usually named after her maternal grandmother - James Sinclair and Jane Fisher's eldest daughter was Mary Wotherspoon Sinclair, so would seem Jane's mothers was named Mary Wotherspoon.
I then looked for a marriage and found on familysearch:
Robert Fisher married Mary Wotherspoon 19/2/1804 Barony, Lanarkshire so this sounds like her parents.
Annette