Actually you are right, I spoke mostly from what I remember and I seem to have remembered wrong. I just went to see the old one again and the new expression is definitely more present.
For the head position, I am not sure that you can render a sense of smallness when you have no reference like the body size or anything else for the eye to compare to. But tbh considering how frail her shoulders and her upper body already look, I think I already got that sense from the beginning, the portrait being on the far end of the frame or not. You can even change the pose (out of the 6-7 ones available) and make the shoulders drop, maybe it can make the body look even thinner.
I don't think the non centered portrait doesn't work though, to the contrary, and I seem to see what you are doing actually. I had a similar portrait early (3/4 face though) entering the frame at the right and looking at the left. No, the more I look at it, the more I find it convincing actually.
Maybe I got all those impressions wrong just because we don't really know what is happening with the shoulders and the arms, it's confusing..
Edit : after 2 hours meditating over it now, I can definitely say it's a good portrait ! The only thing that still annoys me is the shadow eating the right cheek and the upper body pose.
Edit 2 : I don't know if it's just me but does she have an eye always a little more closed than the other one ? It was already the case in your other portraits, and definitely keep that ! It adds a lot.