Road to Paradise — Paullina Simons

Meet Shelby and Gina. Eighteen years old, fresh out of high school, and once best friends. When Shelby gets a bright yellow Mustang for a graduation gift, she decides to drive across America to find her missing mother, who walked out years before. Gina invites herself along for the ride, in a hurry to get to California to stop her wayward boyfriend from marrying someone else.
What begins as a journey of big dreams and high spirits quickly changes course when the girls pick up a young hitchhiker named Candy. Haunted by a mysterious past, she's got reasons of her own to get to California as quickly as possible.
The three girls, uneasy and unlikely companions, find themselves on America's darkest back-roads, pursued by fear and betrayal, and slowly learn they cannot count on anything but each other. The road to Paradise, a story of intense friendship, fierce loyalty, and love, will take them to the last place they expected to be.