Thank you, Warren!
That has my experience too -- all the image searches turned up lots of pictures of the rose, but none of the lady herself. I think it's the rose that will keep her memory alive.
But I did find this one last night, in a page of pictures of her house, Wiganthorpe Hall in Yorkshire. (It was demolished in 1955.)
I assume that's her in the white dress and Queen Mary hat, but just who all those children are the page didn't say. The children of the estate staff? Or is she presiding over a garden party for the village children? Hard to tell -- and even cropped in fairly close the picture is not of sufficient quality to give more than a generic impression of a tall and stately old lady.
Still, my editor may consider that's better than nothing.