I took a look at Scholastic book wizard, but forgot that it may not be enough for you with your daughter's reading level.

Barnes & Nobles has a way to find books by Lexile reading score - that's better.
(http://www.barnesandnoble.com/reading-level-reading-books-lexile/search.asp). You enter a child's age, enter the Lexile score as 1600 or a range, select books (or textbooks or Nook), and then select topic or interest.

Another suggestion is to look at AP reading lists or googling terms like college reading list AND high school so you get lists like (http://www.waldsfe.org/highschool/HAHS/hsbl.htm). Alternatively, you could find reading materials from college courses or typing in specific terms, such as 17th-century European witchcraft reading list or Harvard university history reading list.

I think it might be easier to find books of interest and then see if it matches a Lexile score - provided you're looking around AP, classics, or college-level lists.

One way to get around the dilemma with the advance reading is to see if the teacher allows your daughter to bring in materials from home or public library - rather than sticking with what's in a classroom or school.