I have seen this name (flora) several times related to this family, however, I don't have a confirmed person with this name in the tree.
I know that my ggreat grandfather likely had siblings, but I have no record or names of any. He was born in 1832, so a birth day in 1833 could work. What I have on his father is: Donald Edward Mackay, born in 1804 in Scotland. He died on 15 Jan, 1874 in Rear Lake Ainslee. He was married to a Mary Campbell and that's all I have.
Perhaps my Donald E. Mackay 1832 was a brother to your Flora.
I wish I could help more... I hope you can make some sense of this.