Hello Ace! I'm sorry I don't have a lot of time to verbally explain how I did your paint over, so I must be brief but if you have any questions don't hesitate to ask. I'm sorry I'm also not good with words.
Anyhoo, such a beautiful painting it made me rethink my ethics. XD I vowed never to do paint-overs, but.. what the hell. It's a gorgeous piece and I see so much of myself in it technique wise that it scared me!
So.

What I did using Yian's paintover:
-Added shadows around her eye to hint at the roundness of the eyeball under the lids and skin.
-Added more skin tones towards the temples instead of eyeshadow and used the "Basic Round" brush on Jitter 1 and low opacity to get the glittery effect of makeup to hint at the color instead of coating it.
-Defined the chin with shadows on the neck, though this may be something you want to soften
-Added more forms in the cheekbones to hint at the hollow mouth underneath
-Added more shadows AND highlights to the mouth (check that out, highlight more on the bottom area of the lip, more shadow on the top).
-Gave her some musculature on the brow just above the eyebrows then sculpted the eyebrows to fit the form of her skull.
-Widened her nose and gave more shadows around the eyes and nose, roughly using the tutorial found here: http://www.furiae.com/popup.php?text=nosetutorial (I'm such a Linda Bergkvist Tutorial Link Whore. I know! I'm sorry) Please note that I couldn't finish the nose, as it was the last thing I did. I only found her nose a little narrow as the corners should generally fall under the tear ducts and I think I might have moved the tear ducts in the reshape.
-Widened her lips. I know I might have lost a bit of her expression, but damn I love big lips. Also, didn't finish any texture or adding the glossy wetness Yian did. But he did an awesome job there.
-Redid the eyes and got this.. far off look. x_x I am incapable of making a character look at the freaking "camera".>_<
I realize somehow I turned her almost.. African, with such exaggerated features, so I apologize. I kept thinking of dreadlocks when I saw her hair... Dreadlocks and then the stormy sea made me think of Storm from X-Men...
So. A bit of constructive criticism and a pointer or two, if I may.
1. Just a guess, you're using a photo reference "too much". (Well, not too much, it just seems as if you're trying to duplicate it too hard. Trying to be too perfect).
While photos are wonderful tools, so many beginner artists use it as a crutch (Myself included!). It's the easy way out to anatomy. If the figure is there, why should we learn it? The problem is, we tend to try and only see 2-D. We only "choose" to see certain aspects of a figure. Period. I don't care who you are. The problem with that technique is that we don't strive to understand the colors and shapes that we are trying to represent and therefore they appear "off" or "wrong" somehow or just "not quite what we wanted".
This is why soooooo many artist harp on and on about learning your anatomy - yes. LEARN your anatomy. Learn what the heck is going on, don't just learn the painful names and places of bones and muscles. It does you no good. Understand how they interact to give such shapes to the human body. Screw "parrot" learning as I heard Em call it.
2. As with what I said before, it's most important to get form perfect. Once you understand form, color comes into play.
When dealing with the two at the same time when learning, we struggle to define where form ends and color begins. My guess on why you're having trouble with something 'just not feeling right' is that you're concentrating on using color to express form.
A case example in your drawing is how you are using her makeup to define her eye's socket and lids, not shadows.
Some artists choose to learn how to paint in black and white, perfect the form and then go to color because it's easier to work on one thing at a time. Others use color to sculpt. I think it's a personal preference - there is no right and wrong.
3. This is a personal note XD I noticed... while concentrating on making her beautiful, I can tell you want to erase imperfections. I noticed there are no wrinkles. No beauty marks. Her face is very very smooth. As if you were trying to concentrate on making her look "Barbie" perfect. Barbie is plastic. Barbie is a doll. Screw Barbie.
Sometimes, however, imperfections make us beautiful. I don't care what science says about an "average" of looks.
After all, the importance of beauty or attractiveness in the scientific sense (cause we have to do this scientifically) is to attract the opposite sex, yes?
Well what does the opposite sex like?
This isn't a hard question.
Boobies and 'tocks.
So, by definition she is already beautiful.
Yes, it's that simple. (See Yian's response? XD)
I must be the ONLY freak in the entire world whose perfect would rather have strange features and interesting faces to paint. Perfection is boring- anyone can achieve a Barbie perfection. Real talent, I have found, is making something unique and yours and different.
As a closing note, I would like to say that I see in you real talent and potential and by the way you're striving to better your art, a willingness to learn you have everything needed in the recipe for success. I meant no offense by anything said above, I never know how people will take one of my critiques but please know I did it all with a smile on my face and no malice in my heart.
I cannot wait to see what you do with this, and I am definitely looking forward to more posts from you.