Her forearms are way too thin and short.
What references are you using for your Space girl?Also,there is too much empty space above her.
A smooth sea never made a skillful sailor.
Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so."
Her hands are far too tiny and her legs kind of look more like tubes than legs. They seem like they may be a bit long as well.
Her neck looks a bit short to me, like she is shrugging her shoulders?
And I have no words for this. http://heyyeyaaeyaaaeyaeyaa.com/
The hand not holding the helmet is too far away from the body and too small, and as evidenced by others her legs are a bit shapeless- even if she's meant to have large legs, they'd have a more curved shape because of how muscles are like. Also, there really is too much blank space above her. I'd suggest cropping it so the figure is the focus of the picture and the eye doesn't get lost in all that space.