I am not sure what this animated fantasy show was called. It was somewhere in between 2003-2010 and all I remember is the fact that there were three teenagers, two boys and a girl. I don't remember much about the guys.
She had long ginger hair that was tied up into a ponytail and she usually carried some sort of special book around with her that the group of three found very important. It was also somehow associated with crystals as well, almost as if the crystals needed to be placed into a shape in the book. Either that or the book just had slots where crystals needed to be placed in. The girl also had a monster-like companion that spoke in a human voice, one that literally walked on four legs, controlled vines and was green, like it was covered in leaves or something. I am not 100% sure about this but I think her name was Eden, or somewhere along those lines.
I also happen to remember an episode where the girl had to choose which book was the real book out of a wide selection of similar looking books. She chose the right one since she remembered spilling a drink onto the pages and staining it.