Spellbreaker by Charlie Holmberg 

The orphaned Elsie Camden learned as a girl that there were two kinds of wizards in the world: those who pay for the power to cast spells and those, like her, born with the ability to break them. But as an unlicensed magic user, her gift is a crime. Commissioned by an underground group known as the Cowls, Elsie uses her spellbreaking to push back against the aristocrats and help the common man. She always did love the tale of Robin Hood… Read more.