Esther Blanchett

Firstly I have to say: beautiful. Very well done. I especially love the hair and the eyes.
The nose however, looks a bit strange. I think that's because the nose is more of a triangle (or a trapezium, whatever you want to call it), small between the eyes and broader at the nostrils. this I find is a good tutorial for that: [link]. what's also important to shade a lot between the nose and the inside of your eye, to make sure it doesn't get too flat. The nostrils are very well done, but notice that the shade is reddish rather than brown.
The nun's habit, especially at the top (above the line where the ears would be) is very well done, especially the shading is very realistic. below, I think there's supposed to be much more fabric. It's quite possible it looks this way at your photo, but at this picture of sister Kate [link] (which I know is not Esther, but the Habit is the same) I think you can see quite well that it's broader with more fabric.
Lastly - a tiny thing about the shoulders: they're not the same height. (it could be the fact that it's from a foto - ignore me in that case) I don't think either side is better than the other, but be consistent: either more horizontal like the right side, or more diagonal like the left side.
One last thing (I promise it's the last) I love the metallic sheen at the collar-thingy.(no idea what it's called) It really gives the impression of metal.

I hope you appreciate this critique, and that I haven't offended you, because I simply wanted to help you.

Love, Nicus