Ok before you go on, I suggest fixing the head and face. If you notice in the photograph, her face is at more of an angle and her eyes not so droopy and her jaw line steeper. Also the contours on the right side of her head, or her left come out a little too much.
The rest seems to be descent. Once you perk up the base work, feel free to add more paint. More depth, more contrast. For example slight shadow from her shirt on the left arm and if you notice, her upper chest area above the shirt isn't just a plain solid shade it has bits of darker areas that present fleshiness, that way she doesn't look so plastic.
Good job so far, well done on proportions.
And don't worry, the face is almost always the hardest part.
maybe try gridding out her face to make translating the image to paint an easier task. It could help in visually dissecting the proportions of her face more accurately
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Is this finished? The sketchy lines make it look unfinished, so perhaps clean them up a little, or change their colour to a brown so that they fit in more with the colour scheme of the rest of the image.
Maybe it's just my monitor, but she looks a tad too orange, you might want to try toning down the saturation a little, or using a cooler colour for the shadows.
The texture over the image is a little distracting, I feel like I can't focus on the figure O_o A little texture is definitely good, but perhaps something a little more subtle would work better.
You've made a great start on this, the general idea is there, but just a few little touches would finish it up nicely.
Droopy eyes don't equal sad.
Study your reference more carefully.
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