Hi! I agree with you. I found no mention of where she's interned but maybe this information can help lead you to your answer. This is what I found:
Andrew Noel Agnew, a barrister who had inherited the baronetcy and estates of Lochnaw in Galloway, commissioned this painting of his young wife, Gertrude Vernon(1865-1932), in 1892. It was exhibited at the Royal Academy in 1898 and made Sargent's name. The sculptor Rodin described him as 'the Van Dyck of our times'. Portrait commissions poured in and Sargent enjoyed something of a cult following in Edwardian society. It also launched Lady Agnew as a society beauty.
http://www.nationalgalleries.org/collect…
And this translated (Sorry.. I used Babelfish):
Gertrude Vernon married in 1889 with lord Andrew Noel Agnew de Lochnaw, fifty years greater than its wife. Two years later, his husband obtained the baron title. This appointment can be the reason for the order of this picture, that could be contemplated in the Royal Academy of London in the spring of 1893.
Gertrude Vernon
b. 16 June 1860, d. 3 April 1932, #80231
Pedigree
Father Hon. Gowran Charles Vernon1
Mother Caroline Fazakerley1 b. before 1844
Last Edited 12 Jun 2004
Gertrude Vernon was born on 16 June 1860.1 She was the daughter of Hon. GowranCharles Vernon and Caroline Fazakerley.1 She married Sir Andrew Noel Agnew of Lochnaw, 9th Bt., son of Sir Andrew Agnew of Lochnaw, 8th Bt. and Lady Mary Arabella Louisa Noel, on 15 October 1889 in St. Peter's, Eaton Square, Pimlico, London, England.1 She died on 3 April 1932 at age 71.2
From 15 October 1889, her married name became Agnew.1
Family Sir Andrew Noel Agnew of Lochnaw, 9th Bt. b. 14 August 1850, d. 14 July 1928
