Firebug

Ava is a firebug―she can start fires with her mind. Which would all be well and good if she weren't caught in a deadly contract with the Coterie, a magical mafia. She's one of their main hitmen . . . and she doesn't like it one bit. Not least because her boss, Venus, killed Ava's mother.
When Venus asks Ava to kill a family friend, Ava rebels. She knows very well that you can't say no to the Coterie and expect to get away with it, though, so she and her friends hit the road, trying desperately to think of a way out of the mess they find themselves in. Preferably keeping the murder to a minimum, in Lish McBride's Firebug.