yeah, the first thing I noticed is that the anatomy is wonky, especially the head/face situation. I don't know if you referenced that pose but if you did, look at how the face behaves from this angle. having the locks in the front falling into her face doesn't really help to clarify it.
I made a small breakdown of the pose with better anatomy. The arms are very skinny compared to the rest of the body. I also added the shadow parts if you work from a light source basically directly in front of her
The next thing is, if you colour in things, always be consistent within your piece. You have really much shadow on her skin and the shirt but not on her skirt or hair.
Also understand that any object always has two shadows, the body shadow, and the throw shadow.
The shirt only has its body shadow, the skin a mix of both but also not really. Through that, it's definitely not clear where your light source actually sits. For lighting practice, you can also use so much more contrast between light and shadow.
I tried to show what you can do with a simple glow/lumiosity layer. It's a really quick edit, so not exactly clean but I hope you get what I'm aiming at. Also I edited the shadow on her back a bit because it looked a lot like boobs and I guess that wasn't your intention.
A few tips on digital colouring in general:
The thing I learned about digital colouring is that you don't always need to blend because it makes it look worse in most cases. Clear lines give it more structure and don't wash the effect out. If you want a blending effect nonetheless, it usually looks better to already use a brush that partly blends already while you're painting.
Additionally, backlighting is a really difficult task to start with colour/light & shadow practice. It's positive that you're this ambitious but sometimes it's easier to start with something more simple to figure everything out. I know it's really annoying to hear that because you wanna do the cool stuff (I've been there, too haha) but having the basics down before you start with the complex tasks makes it much easier. In general, try to nail down throw shadows first and then get into the body shadow as more detail. It makes life much much easier because body shadows are influenced by the direction of light and also indicate the texture of an object. If you still struggle with this, it can get really confusing.
The top you're looking for is also called Carmen blouse btw.
I hope that was somewhat helpful and not too harsh ^^;
Anyway, keep on practicing, I think you're definitely on a good way and your ambition can really push you forward.