Ray, I'm not sure if I'm posting this response onto the right thread, but here's a thought.

Working on the assumption that your large lady chauffeur-driven milliner was born and died on the island, and using the likely timeframes for birth and death, I've used Lawson's birth index and death index to match up those female Curpheys who died unmarried.

I haven't looked exhaustively, but I found several candidates. Then I searched for them with their families in the 1891 and 1901 censuses, hoping to find a well-heeled family. None of them looked likely to have been in a position to leave property portfolios to their spinster daughters, with the exception of a Curphey family in Lezayre.

Edward James Curphey (1854-1942 ), miller, and Mary Ann nee Southward ( 1860-1944 ) had 7 ( or more ? ) children.
Edward Southward Curphey 1887
Agnes Isabel Curphey 1889-93
Florence May Curphey 1891-1979
Laura Curphey 1893-1955
Alice Curphey 1895-96
Olive Curphey 1897
John Cubbon Curphey 1900-66

Mary Ann Southward was the daughter of Thomas J Southward, woollen manufacturer and dyer of Sulby.

So 2 possibilities for your elusive Miss Curphey are Florence May and Laura.

If or when you eventually find the real Miss Curphey, please let us know on the bulletin board.

If you're wondering why this intrigues me, it's because your Miss Curphey brings to mind 2 of my grandfather's first cousins, Edith and Mabel Clegg, spinster daughters of William Clegg, builder, of Westville, Douglas. They were born and died in the same era as Miss Curphey, and, like her, were chauffer driven around Douglas in a Daimler. Whether or not they did any rent-collecting I don't know, but they were reputed to have been generous to good causes eg Nobles Hospital.