Michelle, I started last year, when she was in “3rd” with Book One of K-3. I may use Bk. 2 of K-3 next year as my artist “spine” and let her do the projects. Then, the year after that in her “5th” gr year, I’ll start her on Bk.1 of the 4-6 gr. books if she continues to enjoy them.
Since yours is 8, I think you could use Bk. 2 just fine. Since your dd wants to draw actual things, I would recommend getting her the cheap How to Draw… and I Can Draw… books just for that immediate, purely “how to” technique that she needs. Those types of books are what my dd uses to refer back to for help when she draws on her own. I see AP as the big picture, formal, long-term art instruction that will help develop her own artistic abilities.
HTH,
Rachel