It would seem that now would be a good time to have a private and honest conversation with your daughter about her body and sexual behavior. I would have this be a casual conversation in which you give her factual information and answer her questions openly. If you feel as a parent, uncomfortable you can ask the school nurse to assist you or the school guidance counselor, perhaps. There is no shame in asking for help.
Also, note that there are some great books that I recommend:
The American Girl doll and book company makes a great read called the "Care and Keeping of You- The Body Book for Girls" which discusses body awareness when a girl is through her tween and teen changes. It is an easy read and will be engaging to your daughter, especially since she may have difficulty attending. You also can read this together.
Annie Fox, is the author of a great set of tween and teen reads which helps to put what your daughter might be feeling in to perspective - The Middle School Confidential Series is a host of books that she has written that are very visually attractive and chocked full of great information.
"Dear God It's Me Margaret" is a very famous and often cited book about girls becoming women and is written by Judy Blume.
In addition, If you go to www.AnnieFox.com your daughter can ask any questions she wishes on the Ask TERRA portion of the website.
You as a parent also can access parent information there, too. And by all means continue to look around on Education.com for information that you seek.
I wish you and your daughter well. I know that you mentioned she is ADHD, however note that tweens and teens ALL of have questions about this stage of their lives.