Road To Paradise by 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 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 backroads, 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.