Mary is in the background of the painting by Terence Cuneo of her father receiving his Victoria Cross from King George V in 1918: https://artuk.org/discover/artworks/presentation-of-the-victoria-cross-to-the-reverend-theodore-bayley-hardy-vc-dso-mc-by-hm-king-george-v-18651936-24282
Information kindly supplied by the Museum of Army Chaplaincy
near Andofer, Hampshire, UK http://www.army.mod.uk/chaplains/23363.aspx
Sources:
http://1914-1918.invisionzone.com/forums/topic/252032-26th-stationary-hospital-ismailia-egypt-ww1