The Second Summer of the Sisterhood (Sisterhood #2) by Ann Brashares

With a bit of last summer's sand in the pockets, the Traveling Pants and the Sisterhood that wears them embark on their second summer together.

Bridget: Impulsively sets off for Alabama, wanting to both confront and avoid her demons... but she can't keep the truth from the Pants. Carmen: Is concerned that her mother is making a fool of herself over a man. When she discovers that her mom borrowed the Pants to wear on a date, she's certain of it. Tibby: Makes a movie she'd like to be proud of... while the Pants keep alive the memory of a friend who could see beyond appearances. Lena: Has spent months hiding from love... only to find that she's at last ready to put on the Pants and let them lead her where they will.