The Last Girls Standing by Jennifer Dugan

Sloan and Cherry. Cherry and Sloan. They met only a few days before masked men with machetes attacked the summer camp where they worked, a massacre that left the rest of their fellow counselors dead. Now, months later, the two are inseparable, their traumatic experience bonding them in ways no one else can understand.

But as new evidence comes to light and Sloan learns more about the motives behind the ritual killing that brought them together, she begins to suspect that her girlfriend may be more than just a survivor–she may actually have been a part of it. Cherry tries to reassure her, but Sloan only becomes more distraught. Is this gaslighting or reality? Is Cherry a victim or a perpetrator? Is Sloan confused, or is she seeing things clearly for the very first time? Against all odds, Sloan survived that hot summer night. But will she survive what comes next?