I did find out the following if it helps.
Helen Knibb was born in Kettering in the autumn of 1885 and died in Lewisham aged 33 in the spring of 1919
Inscription on memorial at Lewisham:
STONE: DEDICATED TO THE BRAVE MEN WHO DIED IN THIS HOSPITAL AND LAID DOWN THEIR LIVES FOR THE BRITISH EMPIRE 1914-1919. AND TO DOROTHY GOODMAN AND HELEN KNIBB WHO DIED AT THEIR POST OF DUTY NURSING THE SICK AND WOUNDED / ERECTED BY THE MEDICAL AND NURSING STAFF LEWISHAM MILITARY HOSPITAL