Working around Margaret being born c. 1840 in Angus, there is this possible 1871 census entry:
Margret Boath 30 flax dresser b. Arbroath
Maria Connoly 37 boarder b. Dunfermline, fifeshire
Isabella Boath 30 boarder flax dresser b. Arbroath
Georgana Christer 7 boarder b. Arbroath
Address: Lawton Mill Private House, Inverkeillor Angus
Although showing as a boarder in the household, 7 yr old Georgina looks to be daughter of Margaret, see FX index entry
www.familysearch.org/ark:/61903/1:1:XY5J-JZR (original image on SP).
There is also a Margaret Booth, aged 18 and born in Arbroath on the 1861 census in Inverkeillor. She is showing as a servant and millworker at 4 Boysack Mills Bothy.
Monica