The Shapeshifter's Secret Series by Heather Ostler

Like any sixteen-year-old, Julia's used to dealing with problems. From her overprotective father to her absent mother to a teacher who definitely has it in for her. But everything changes when Julia's reactions become oddly vicious and angry---more animal than human. This action-packed adventure has it all: humor, romance, and a plot that will keep you guessing to the very last page.

Julia’s life has gone from complicated to nearly impossible! When Julia loses her shapeshifting powers and her appearance changes in alarming ways, she flees to Sirenity, where she learns an incredible secret about her mother. In this thrilling sequel, Julia must take greater risks and make bigger sacrifices as she discovers who she really is and what she can really become.