I have now been through the Electoral Rolls for the period after 1921 until the Almshouses become vacant.
I have not found any
Mrs Coleman registered at this address.
From the photo it appears that the lady is standing at the doorway of No 100, which seems to have been the last one occupied, but on the ER by
Mrs Agnes Gilbert who had been there at the 1921 census until her last reference in the ER of 1929, although she actually died on 2nd Oct 1928.
I guess I'll never find out who captioned the photo shown in "Rickmansworth: A Glimpse of the Past" and how Mrs Coleman was named.
http://www.hertfordshire-genealogy.co.uk/data/books/books-2/book-0296-rickmansworth-glimpse.htmI am intrigued by your reference to the "Valuation Survey of ~1910", is that generally available online??