The Stone Keep by S. K. Marlay

Eadha learns early the cruel nature of the world from Lord Huath, a brutal
Channeller. The Channellers rule Domhain, sapping magic from others so that
the crops might grow, the cities might prosper, and the dragons might be held
at bay.
But there is another, more ancient power blossoming in the young Eadha, one
that does not consume the life force of others. And as the world and its
cruelties rush toward Eadha and Ionain, the boy she has always loved, she
faces a terrible choice: make a lie of Ionain’s life or watch him lose everything.