As someone who grew-up in the gifted programs from the age of 8 on, I'd personally say ANY kind of reading is good. If she only focuses on a certain length of book or genre, it may get old and undesirable. But, if she mixes it up with her old books, she may be revisiting fond memories, reading from a different point of view, or using more of her imagination in going through the stories again.
My husband is much more an avid reader than I am (I am slow and conversational in my reading), and he just wants the kids to develop the love of it.
I'd offer her as many options as possible to continue to foster and encourage her love of reading. If you force her in one direction, she may begin to resent it and move away from it all together.
I have certain genres I prefer (more science based), my husband has others. We have an eclectic mix that we'll encourage our kids to explore as they get older.
Don't forget to let her be an age-appropriate kid, too. I feel like my parents made me miss a lot of my childhood by trying to get me toys/gifts that were more conducive to my intellect than letting me just be a kid sometimes. If she's truly gifted, she'll have the curiousity and drive to continue to push herself on her own.
Good luck and congratulations on having an exceptional child.