I'm going to preface this with a few bullet points. A) I am a 2D Animator by trade. B) I've just begun to get into digital painting as a serious side skill. C) I'm not yet at this skill level, but may be able to contribute some food for thought coming from a different area.
First off, the composition is sensible. Our focus is slightly off center and well framed by the downed ship behind her. Even the dead guy on the ground is facing the focal point so everything in this piece is unified in leading our eyes towards what you want us to look at most.
I would say the weakest thing here is her pose. Both her legs are so similar that they might as well be a flipped duplicate of each other. The silhouette and pose would be better with less symmetry there, perhaps the left leg (audience left) further out in profile. Secondly, her left arm could use some refining. Were her silhouette blacked out and all BG elements removed, I would think someone is pulling that arm. The rest of her body reads as exhausted, but that arm is doing something else entirely. Resting her elbow on her left quad would really add to that post carnage exhaustion I think, like she can barely hold her body up anymore.
This is a small thing. To her right reads well as a helm, but I'm not sure what the object to her left is. It also creates a bit of tension being so close to her body but not quite touching. Almost a tangent I guess.
Last little thing. She is decked out in body armor, but her shoulders are exposed. What you have is more practical than 99% of artist's drawing women in armor, and I love that. Why not go that last step, and give her some shoulder pads, or even turn her skin tone to metal to match the rest of the suit? Otherwise, her weakness is too obvious to her enemies.
Everything else reads well. I like the negative space around the hand aimed at the ground, love the colors and expression in her face, and that little blue wave on the ground around her. I'm enjoying your work, and am very inspired by it. Thanks for sharing!