Magic. The Endonshan Chronicles, #4

Young Princess Tashan loves life in the palace with her parents, as well as sneaking out in disguise so she can play with her older cousin, Ari. Her biggest problem is trying to control her untamed magic use - or it was, until she stumbles into a plot against her family and is kidnapped. Staying disguised as a street kid, she struggles to find a way to escape with no one to help her but a grandmotherly elder and a pugnacious teen.
Unfortunately, there's only so much they can do locked in an underground dungeon, especially when Tashan's magic is more likely to harm them than to do anything useful. An unlikely ally arrives with a new possibility for escape; the only catch is that the plan hinges on Tashan's magic. If she can't come up with a way to control her magic use - fast - then she'll lose her parents forever.