For 's I'm Sorry, But...
They asked for tips on proportion, lighting and shading.
The top part is more on foreshortening the face and how those proportions would work. You did a great job with what I like to call "squishing up the face." However, everything was a bit skewed from the middle of the face. Remember: guidelines are your friend!
Also, it seemed like she was looking at the heart, so I tried to find a reference of someone looking down. If someone is looking down, you wouldn't see much of their eyes, if at all, depending on how far down they're looking. If you look down, your eye lids will just naturally close a bit. Also, I said it in the picture, but if someone looks down, their neck goes out a bit too. If it didn't do that, the neck would get squished up, so because of this the neck would be foreshortened as well, and the head would hide some of it. So you wouldn't see much of the neck.
As for lighting, I wrote down some questions you should ask yourself when you're ready to shade:
1) How many light sources do you have?
2) Where are they coming from?
3) Which direction are they going?
4) What does it hit?
5) What blocks it?
If you notice, I drew in some lines showing the direction the light is going in. (I just assumed the light source was the heart because of some of the blue lighting you had) Now, with only one light source, the lighting and shading would be very harsh on everything it touched. Think of holding a flashlight up to your face in a dark room.
In your original picture, it looked like there were some tears drawn on her face. To help accentuate that, you could highlight them. Since they are water, they would reflect light very well.
I think that's all I came up with, if you have any questions on some of my comments, don't be afraid to ask.
Artwork belongs to NanokoAishino
Correction belongs to ME