The entire series is so good that I, a self-confessed book hoarder, consider them one of the few books I will give away just to spread the joy of it.
Might I suggest gifting her some books to go along with it:
The Wee Free Men: A book about a young girl named Tiffany Aching going to the land of the fairies to save her little brother.
A Hat Full of Sky: Tiffany begins her training as a witch while being possessed by a spirit from before time and space.
Wintersmith: Tiffany causes quite a stir when she participates in a season changing ritual inadvertently becoming the avatar of Spring and having to fend off the advances of the spirit of Winter.
I Shall Wear Midnight: Tiffany, now recognized as The Witch of her homeland, performs various duties while helping her peers.
The Shepherd's Crown: After the death of her mentor, the strongest witch, Tiffany helps a young man who wants to be a witch, the deposed queen of the fairies, and anyone else who needs help as she is now recognized as the strongest witch.