[Rizla]

The Tripod trilogy by John Christopher (not very spacey, but super-cool). All the Doctor Who books. You could swap the genders with a bit of thought.

The Amber Spyglass / The Northern Lights (the first book) has a female lead. Again, not very spacey (and not very young adult).

Have Spacesuit Will Travel by Heinlein. I read it as a good and loved it. All in the first person. Change the gender. Also Islands in the Sky by Arthur C Clarke. All kid's stuff, unlike some of the above stuff IMO.