Liam Payne’s girlfriend, Kate Cassidy — who was with the One Direction singer just days before his death — is reeling from the tragic loss. A friend of the influencer exclusively told The Post that Cassidy is agonizing over her decision to leave Payne alone in Argentina before he fell to his death.

A source close to Kate Cassidy tells PEOPLE exclusively that Liam Payne's "erratic behavior started ramping up" when she left Argentina, where they were on vacation. The One Direction alum died on Oct.