Both of Us by Amber Kelly

After running away across the country, Brie Masters is finally settling into her life in California. She’s surrounded by loving friends and her brother, who is there to keep her safe—specifically, to protect her from a man from her past who won’t let her go.
But, as the danger starts affecting those around her, she flees back home, back to the life of Gabby Mastreoni.
When her stalker goes after the one thing that could hurt her forever, she has no choice but to run to the last person she wants to ask for help. And then all of her secrets will be exposed.