I've just looked her up on the Oxford Dictionary of National Biography - dates differ 1872-1950; maiden name given as Rayner. Born Preston as second of seven children, father Alexander Clement Rayner (1841/2 - 1916) a surgeon & mother Mary ("Polly") nee Pilkington Sharples (no dates stated). According to the piece her husband was Charles Samuel Alfred Rigby (1858-1926) a doctor - marriage 1893. Also the article states they adopted a two year old (Arthur, known as Sandy) in 1905. It gives her death as at Erdmouth 23 July 1950.
They reference as a source "My Aunt Edith" by P Hesketh.
I wonder if Arthur/his family would be considered descendants by the Probation Trust? If the ONDB is accurate there seems to be no blood-line direct descendants.