Forgotten Women: Sister Mabel of the Free Dispensary for Animals of the Poor

The Free Dispensary for Animals of the Poor was run, starting in the early 1920s, under a railway arch in Camberwell (south London) - four hours a week when the poor could bring their pets to be treated for free by a vet. It was started by a woman described only as "Sister Mabel", who'd raised the money from "Lord Hertford".

I've not been able to find any web references to it, but read about the dispensary in H.V. Morton's The Spell of London, first printed in 1926. They are collected sketches from the Daily Express (a very different, far more humane paper than its modern sister) and do lay the pathos on with a trowel, but are gripping nonetheless.

I watched this for an hour: pups run over by motor-cars, dogs with mange and distemper, and always such love, such tender looks, such tail waggings from the dogs, until -
"Please, mother says will you have Arfur killed, 'cause the lady upstairs says she'll turn us into the street if he don't stop barkin'."
Arthur, a nice little fox terrier, stood there with his head on one side, so pathetically unconscious of crime, so pleased with life, and - so near death.
"You can't kill him?" I said.
"We do our best not to," said Mr Murt [the vet]. "We have a register of those willing to take dogs. We keep these poor little chaps and try to find them homes, but if we can't ... it's better than having them kicked about in the streets starving."

Has anyone else come across Sister Mabel?