.....Model placement in your chosen composition can make or break an image. I tend to place models with darker skin tonality closer to the brighter light sources.

On this first shot, Krystal has fair skin, but darker than Anya's, so I would rather have Krystal remain in the forefront as Anya's skin act as

a (reflected) fill light in her shadow areas and keep the overall tonality within the cameras exposure value. In the second image,

I did not think too much about it and the shot suffered a bit of washout in the white areas and a bit of muddyness in the darker areas for placing

the light in the opposite direction.