Rihanna and Cara Delevingne are reportedly a "lethal combination" when they're together.
The pair are famed for letting their hair down when they meet up, often attending parties until the early hours.
While people have speculated that 20-year-old Cara is being influenced by Rihanna's ways, a source has revealed that they are both as bad as each other.
"Everyone thinks Rihanna is a bad influence on Cara Delevingne. But the truth is, together they're a lethal combination - they're always the last ones standing when they party," a source told British magazine Heat.
"They push each other to the limit."
Rihanna was two-and-a-half hours late for a recent show in Birmingham, UK, after leaving a London nightclub with Cara in the early hours of the morning.
The pair are said to be planning to spend £500,000 on a lavish holiday and are apparently travelling around the French Riviera in a luxury yacht.
"It will be no-holds barred and they're spending more than half a million on the yacht rental and on going to top clubs and restaurants," a source said recently. "It'll be non-stop booze and they are already saying they're not going to get much sleep - maybe a couple of hours each night."
Rihanna, 25, has also reportedly invited model-of-the-moment Cara to spend a long weekend at her home in Barbados.