Hello,
I realize my response to your post is 10 years after the fact, but maybe others in the Q&A section might find my post helpful.
Before she starts mensurating and if you're planning to use sanitary pads, I would recommend that she be introduced to wearing them prior. I started my daughter with the panty liners and it helped with the transition.
I also got these books to help with the conversation. The Care and Keeping of You: The Body Book for Younger Girls, and The Care and Keeping of You 2: The Body Book for Older Girls. Author is Josee Masse.
Best of luck to you!