Kiss Me with Lies by S.M. Soto

Two sisters. One unsolved murder. A sickening plot for revenge.
When Mackenzie Wright attends her first real high school party, held somewhere deep in the woods of her small California town, no one expects to wake up the next morning to news of a gruesome murder. Especially not her own sister’s.
No suspects.
No motive.
No convictions.
Just one unsolved murder and whatever’s left of the now deserted town.
Mackenzie has spent years with her sister’s death weighing heavily on her shoulders, but it isn’t until she stumbles across a photograph that changes everything for her. The memories, everything from that night, come flashing back in high-speed technicolor and Mackenzie soon finds herself obsessed with the truth.
Determined to find out what really happened to her sister, Mackenzie relies on that one photograph to give her the answers she needs by embedding herself into the lives of five of the wealthiest men in Los Angeles. Consumed by her need for revenge, Mackenzie infiltrates the world of the rich and elite, only to come face-to-face with an alluring complication in the form of an elusive playboy.
When enemy lines are drawn, Mackenzie has to choose between her loyalty to her sister and the man who has stolen her heart.