If I recall correctly from the practice book, the science seemed more reasoning problems. It didn't depend on prior scientific knowledge. I think it would require that one be able to read quickly and assimilate information and draw conclusions quickly. But then again, we are a science family so what seems obvious to me, is probably not to others.
My DS sounds similar to your DD as far as testing. I'm not holding out any hopes for high scores on the Explore but it was a good, positive experience for him. He too would rather work it out in his head than have to pick up a pencil but he'd be faster if he did it on paper w/ fewer mistakes. He's also perfectionistic about math (I think from never being challenged in school and never getting anything wrong - now even w/ a year of HSing under his belt, if he misses a problem he shuts down to that topic).
