You Owe Me a Murder oleh Eileen Cook

Seventeen-year-old Kim gets more than she bargained for when she is set up for murder. Perfect for fans of One of Us Is Lying, E. Lockhart, and Gillian Flynn.

Kim never expected to plot a murder. But that was before her boyfriend dumped her for another girl. Now, Kim’s stuck on a class trip to London with him and his new soulmate and she can’t help wishing he was a little bit dead, even if she’d never really do that.

But when Kim meets Nicki, a stranger on the plane who’s more than willing to listen to Kim’s woes, things start to look up. Nicki's got a great sense of humor, and when she jokes about swapping murders, Kim plays along—that is, until Kim’s ex-boyfriend mysteriously dies.

Blackmailed by Nicki to fulfill her end of the deal, Kim will have to commit a murder or take the fall for one.