For fantasy, “The Belgariad” and “The Mallorean” sagas by David Eddings were amongst my favourites when I was that age, and the “Magician” books by Raymond E. Feist. My ex-wife introduced me to the work of Robin Hobb and Cecilia Dart-Thornton, both of whom are excellent. “Mistborn” by Brandon Sanderson will probably be an all-time favourite, it is for me and my partner! I also loved the Myth books by Robert Aspirin, for a lighter read, and I’d be remiss if I didn’t mention basically anything by Lawrence Watt-Evans. His Ethshar books hold a special place in my heart.

I’m so happy for you that she likes science fiction too! Iain M. Banks’ “Culture” series is great, and of course The Dragonriders Of Pern by Anne McAffrey is a classic. Lawrence Watt-Evans again, he wrote “The Worlds of Shadow” trilogy which is a neat blend of science fiction and fantasy. There’s also The Dark Tower by Stephen King which I read around 11 or 12. It’s great, but maybe a bit dark which I’ve otherwise tried to stay away from in these recommendations.

Speaking of dark, for when you feel she’s ready: Joe Abercrombie’s “First Law” series is some of my favourite dark fantasy I’ve ever read, but man is it grisly.

Edit: How did I forget Pratchett?!? And by extension, Neil Gaiman. “Good Omens” is a brilliant read, and the series adaptation is excellent too. There are just too many good authors to recommend in threads like this, which I guess is a good problem to have!