The Truth of Letting Go — Amy Sparling

The summer before senior year, Lilah Monroe's parents take a nine-day trip, leaving her as the guardian of her bipolar cousin, Cece. When Cece's parents died tragically five years ago, she and her brother moved in with Lilah. Her brother soon went missing and was presumed dead.
Lilah and Cece couldn't be more different. They used to be best friends, but high school has changed them both. Lilah likes order, schedules, and a tidy room. She has plans for her future and won't let anything derail it, not even Cece whose life is constantly on the edge of chaos. Cece is messy, erratic and sensitive. She also has a reason to believe that her brother is still alive. Despite Lilah's reservations, Cece tracks down an old friend who believes her theories. Ezra happens to have gotten really handsome since Lilah last saw him. Too bad they never really got along when they were kids.
Knowing the odds are stacked against them, Lilah breaks all of her parent's rules for order and reason and joins forces with Cece and Ezra to set out on the road in an old RV in hopes of finding her dead cousin. Lilah and Ezra have a love connection amid the chaos, and when they discover what really happened to Thomas, it's a truth no one saw coming. One that just might get them killed.