Thanks. It always helps to know roughly which century to look in.
Gleneagles is in the parish of Blackford.
See the screenshot, which lists all the El*bet* Proudfoots born between 1910 and 1920. None of these places is in Blackford or indeed in Perthshire. There are in fact no births or marriages of any Proudfoots in Blackford at any time from 1855, and only one death, a 79-year-old Elizabeth Proudfoot or Bayne in 1900; but the only Proudfoot/Bayne marriage is Thomas Proudfoot to Catherine Bayne in Methven in 1868.
There are no El*bet* Proudfoots in the 1921 census anywhere in Perthshire, and no Proudfoots in Blackford in any census from 1841 to 1921. There are four Proudfoot children in 1921 in Auchterarder: Robert A, 12; Margaret, 11; Archibald, 10; and Jessie A, 6; but no adult Proudfoots.
The three younger ones match the births of three children with mother's maiden surname Anderson: Margaret, 1910, in Forgandenny; Archibald, 1911, in Kinnoull; Jessie Anderson, 1914, in Forgandenny. The most likely marriage is Archibald Proudfoot to Jessie Anderson, 1909, in Forgandenny. I think Robert was probably born before his parents' marriage as there is a birth of Robert Anderson, mother's name not indexed, in Forgandenny in 1908.
Archibald Proudfoot, native of Forgandenny, son of William and Jemima Proudfoot of Auchterarder and husband of the late Jessie Anderson, was killed in France on 26 July 1918. Jessie Anderson or Proudfoot, 35, died in Forgandenny in 1914.
I also looked at the Valuation rolls. There are no Proudfoots in Blackford in 1920, 1930 or 1940. The closest matches are a Robert A Proudfoot in Aberuthven and a Lindsay A Proudfoot in Lennox Cottage in 1940. Both of these places are in the parish of Auchterarder, not the parish of Blackford.
Lindsay Allan Proudfoot married Annie Morrison Alexander in Perth in 1901 and they had two daughters, Mary and Christina, born 1902 and 1905 in Perth. So he can be discounted.
The earliest marriage of a Robert A Proudfoot is in 1937.
So I have to admit to being stumped so far.
Unless .... there is no death in Scotland of Jessie Anderson Proudfoot, born 1914. Maybe your Elizabeth is Jessie, who has slightly adjusted her name and where she came from? Gleneagles is generally thought of as being near Auchterarder, so it's not a huge adjustment.