I hope this is helpful...
I haven't seen any of the books, but from everything I've heard/read she is a positive role model for girls age 6 to 14. Her show is about family, life and it's funny, too. A real family program. I think the books would be a good choice. Clothes? I would go with jeans, multi-striped socks in bright colors which pre-teens love, or a pair of colored jeans and a sweater in a coordinating pattern and a matching pull over cotton long sleeve t-shirt The color ensemble will cost you for 3 pieces, and it will give her a sweater & jeans, a t & jeans, cold weather layers, she can wear the top & sweater with denim jeans. You know, mix & match pieces which will give her several outfits from the one set.