You may not be good at photography, but you are amazing at acrylics!
I love the colors you used, and the various shades of blue. The ring around her eyes is very interesting and adds a sense of mystery to the subject. I love the shadings on the skin tones, they look very natural and realistic. Her left arm looks a little funny to me, like it is withered at the end. Perhaps it should have been a little larger? The details are very well done, and I especially like how you did the highlights in her hair.
I think the red flower, being such a different color from the rest of this piece really stands out and is a very nice touch.
I'm sure there was some artistic reason for painting the blue triangle on her nose, but personally, I find it rather distracting. But that's just my humble (and I mean VERY humble) opinion.
I love how you did her eyes. They are quite mesmerizing, and so well detailed. I know how hard this must be to achieve with acrylics, at least for me!
The hint of blush in her cheeks is a very nice touch, and keeps her skin from looking too sallow. This was very nicely done, and blended so very well!
Overall, this is one amazing, and well done portrait. The composition is great, and your painting style is superb.
I look forward to seeing more of your paintings. You have a real talent for it!
You're dealing very well with acrylics, especially for a third painting! This picture is heading towards realism, so my critique and advice will head towards it, too.
On the technique. You already know how to gradient smoothly, like on her back. I'd consider making the background more in this manner, instead of vertical brush lines - while in the right part it goes nicely with the model, on the left it distracts from her, especially the strong diffrence between the really dark shadow and the brighter green. A smooth gradient would do much better in this place - and if you controll it, making it the most blurred in the left border, you can achieve a sence of depth, like the lady was standing by a wall, at a certain angle.
About her hair, try to use the same smooth gradient as a base, and then add the subtle lines.
Consider anatomy. When drawing anything living - a human, animal, perhaps an alien - always try to imagine how it would look like when moving. Imagine this lady straightening her arm, her palm and fingers. What do we get? Her forefinger is too long. Take a look at your own hand - you can easily see that in a healthy hand the middle finger is the longest, then the ring-finger is a bit shorter, and then we've got the forefinger. I recommend taking a look at this tutorial, it's very helpful. A hand is one of the hardest parts of human body to draw and despite the mentioned issue, you've done it nicely anyway.
You've shown that you're not afraid to use darker tones on her body, don't hesitate to use them around her nose, too, especially at its bottom, to make it stand out more.
Also, her back seems to lack a shading that would mark her spine. With this pose, it should be visible in the bottom right corner of the painting. This would also break the plain skin gradient and make it more interesting.
What do I really like about this painting, it's that you've used spots of red/burgundy colour to grab the viewer's attention to her face, along with the well staning-out eyes. Her lips, eyes and the flower are the best painted part of this picture, so you've picked up the focal point very well.