Hmm.
I looked on Scotlands People and there are no Minnie McGills born in Falkirk. Or at least, if they were born in Falkirk, they were registered somewhere else.
It offered me 3 matches on a soundex search for a female birth of Min* Magill born between 1865 and 1880, these were:
1868, Mina Anna McClew, b. Portpatrick, Wigtownshire
1876, Minna McGill, b. Glencairn, Dumfriesshire (so the one on the 1881 Scotland census)
1879, Minna Michael, b. Newington, Edinburgh City/Midlothian.
Newington is the nearest one to Falkirk - but still 30 miles away!
Ancestry is down, otherwise I'd help look fo Minnies in Falkirk 1881. And Scotlands People is very slow, I think everyones out doing 1911-based lookups

Barbara