I taught a high school astronomy class not too long ago, and used
"Astronomy Today" by Chaisson and McMillan. It's every descriptive and covers everything from the history of astronomy all the way up to astrophysics. And while there is some math in it, it's not super-advanced math. The school where I worked didn't like it - they and some of the students complained that the class was too advanced for a high school elective. I would have put it around a college freshman level, but I refuse to teach a science class that doesn't challenge the students, so I stuck with it. If she's really into the Astrophysics aspect, try "Astronomy and Astrophysics" by Zelick and Gregory. Definitely a college level book, but still very readable.
Many communities have an amateur astronomy club - maybe you can take her to some of their meetings?
