Terras: Book 1 of The Tree of Tales

The safety of her rural, teenage life evaporated the moment Abby stepped through the mist.
Her reality is shattered when she discovers that Dreamers from Earth created the mythical beasts, Gods, and legendary heroes in the magical realm of Terras, forging the basis of the only civilization she has known.
Accompanied by her grandmother and two small dogs, they venture toward the fabled Tree of Tales, guided by an irresistible force, and encountering powerful friends and foes along the way.
Threads of a sinister plot against the Tree slowly unwind, while frightening psychic powers begin to awaken within her mind. Forbidden knowledge and ancient wisdom are forced upon her fragile psyche that threaten to utterly change her view of life and her place in the universe.
It soon becomes apparent; the only way home is to save the Tree from dark forces bent on its destruction.
For that, she must speak with the dragons.