I'm "old" enough to have waited for all but the first book to come out before I could read them, so the the timing of the books was much different than it would be for your DD.
I started reading the books in K, and I know I got many of the names of characters and spells horribly wrong the first few times I read the books, but it was always nice to see how much more I understood each time. Especially when I got older and was able to make connections to mythology, I found out there is much in those books to discover at any age. Though I could always read the words, what I could grasp changed over time. I think it was also helpful to experience the scary stuff through a book that could be put down for a while rather than facing it in real life -- it gave me more time to think about what the sacrifices meant and how the search for power can change a person.
If you haven't already, you could maybe read the books at the same time as her so you have an idea of when tough issues may pop up. Or you can alternate reading each other chapters so she can ask questions as you go along and draw the process out a bit.
