Mabel had two brothers who volunteered for duty early in the war Harry Guthrie Whishaw and Bernard Guthrie Whishaw. Harry was killed in action on 3 July 1916 at the Somme and Bernard died of malarial pneumonia on 17 October 1918 in the Middle East. I imagine that both her brothers were at the forefront of her mind while she cared for the soldiers who returned from the war to Featherston Hospital. For their parents it must have been heartbreaking. Sadly more heartbreak followed when Mabel succumbed to the influenza epidemic on 10 November 1918 (one day before armistice) she likely contracted the disease from the very patients she cared for. She was given a full military funeral (see link below).
As a post script to Mabel's story she was also immortalised on a plaque in memory of nurses who served during WW1 erected at the Elizabeth Garrett Anderson Hospital in Euston Road, London in 1938. Elizabeth Garrett Anderson was the first English woman to become a medical practitioner. The hospital opened in the 1870's to allow poorer women access to medical care and was renamed the Elizabeth Garrett Anderson Hospital in 1918 after her death.