Just an idea....
Use some of the tones that you have already to start.
Block in her shape with one of those mid range purples.
Block in the light hitting her back (if she's facing us) and dont put any information or value range in that light unless it is edge information.
And use the reflected light to add details (aka soft and hard edged) secondary information to the shaded area that would be facing us.
Frame her in that closest window since it is in just the right spot.
This way she will be a dark figure on a light background in the comp, and her shadow side will be detailed with your reflected light information.
Hope that helps.