In 'Laura Knight at Theatre' (Unicorn Press, 2008) Timothy Wilcox writes:

The figures in this dressing room scene have not been conclusively identified, but the foreground figure is likely to be Lopokhova, in the costume of Columbine in Carnaval. The flounced dress was decorated with a motif of cherries around the hems, which Knight, as often elsewhere, renders more simply.