Dear Sophie,
I love your portrait. Great job.
I'm not usually home this much but this month I'm painting about 20 pieces for donations and I have to get them done before my 'busy' time of the year. But I'll tell you my thoughts on your painting. But I want you to realize that you should only take to heart what the other experts say that are on SOG. But I'll give you my opinion anyway.
First, I love the portrait. What would I do differently? Actually without seeing this in real life it is hard to judge but I was wondering, when you added the lighter accents to the skin, did you mix any yellow into the highlight color? If not then it looks a little bit chalky which is kind of cool because you said that you are also a pastel artist.
Anytime that I mix white with any paint then I like to add a little bit of yellow to keep it from looking too chalky (with the exception of the violet hues). The rule is to add the color above it on the color wheel toward yellow when adding white to any color. But with the flesh colors I usually add a tad of yellow. I learned this from Jerry Yarnell's video on color mixing.
He also suggested mixing skin colors from a base of Alizarin and a yellow green mixture. I find that this is livelier than some of the other 'tubed' flesh colors (but then again, I haven't tried that many of the others,just over the counter ones).
And, of course, as I said, your picture online looks a little chalky on some of the lightest facial areas. Sometimes when we make photos of our work then the lighting in the studio will also make it appear a different color.
The only other thing that I could say is that the dark shadows that are located on the bottom of the neck seem a little too dark. But again, with pictures and scans and photoshop tools, then this might not be as it is in real life.
With that shadow being one of the darkest values in the whole painting, then it pulls at the eye a lot. And maybe if they were lightened a little then there would be a smoother transition so that it wouldn't pull the eye so much.
Actually if there were somewhere on the neck that you could reflect the lightness of the shirt (and making sure that it didn't emphasize lose skin) then that would make a really nice transition there.
That's all I'm going to critique about your wonderful painting. It was so fun to see it and you are very talented. Congratulations on a beautiful job! I love his look.
Remember that my opinions are not to be taken as one would take one of the SOG experts though. They really know their stuff here.