I remember now that whenever I go away from painting for a time, it takes me a while to regain lost ground in the mixing and applying skin tone. I reviewed a workshop video that I own, but my results based on his technique are just too dark for my taste. One of his rules is (and a common one, apparently): never put white in the (warm) shadows, because white cools. I just don’t know how one gets that to work with a high key painting. The other half of my problem is that I am “fixing” a photo with flash.
Anyway, I’ve gone to look at some Singer Sargent paintings. I’ve read he always started with the middle ground, rather than starting with the dark. This may work better for me for this painting. I can’t swear to it, but his shadows may even have white in them…