The Ends of Things by Sandra Chwialkowska (Author)

As soon as they arrive at the Pink Sands resort, Laura and Dave are handed cocktails garnished with umbrellas and led to a luxurious suite. It's a lovers' paradise. But when they head down to the pristine beach, Laura notices an oddity among the sunbathing couples: a woman vacationing alone. Intrigued, Laura befriends the woman, Diana, and as they spend time together, Laura finds herself telling Diana secrets she's never shared with anyone.