There's a Mary Coulthard, service number 3296, "To be Asst. Sec. Off.s on prob. (emergency) - 20th Nov. 1941" in the LG of December 9th 1941, p.7001.
Could be the same W.A.A.F., perhaps?
An account of the incident at Kenley record she was injured by a tin helmet, which badly cut her leg: