Trixie on Family Tree Circles

I am trying to research my family who originate from Scotland Isle of Arran area. I have so far traced

John McMillan married Mary Gilmour 28.11.1891 in the District of Greenock Renfrew Scotland. John's father was called Thomas McMillan and his mother Barbara ?Cook?
It appears they had 6 children Alexander Gilmour McMillan 1901, Ann McMillan 1905, Elizabeth Annie McMillan 1896, who was my grandmother and she passed away in 1967, Mary McMillan 1900, Robert McMillan 1909 and Ronald McMillan 1904.

Elizabeth Annie McMillan married John McAulay on 5th October 1916 in the District of Shiskine County of Bute Scotland. John's father was called John McAulay and his mother Mary McPhail both deceased by 1916. Elizabeth's parents were called John McMillan and Mary Gilmour.
They had 4 children John McAulay 1917, Barbara McMillan McAulay 1918, Mary McAulay 1924 and James Brownlie McAulay 1934.
When the family moved to England in the 1930/1940 Barbara remained in Scotland and was married to an army officer. We would presume she remained there as all contact was lost. Can anyone help us trace her or her remaining family?