Rihanna and Cara Delevingne became friends when Cara slapped the singer's bum.
The 'Valerian' co-stars are incredibly close and Rihanna, 29, says that while their friendship had a playful start, she knows that she can turn to the model-turned-actress for anything.
Speaking to the Sun on Sunday, she said: "We get silly with each other. The first time we met was because she came up to me and slapped me on the bum.
"But myself and Cara are incredibly close. It's portrayed like we are just party buddies but there is much more to our friendship. She is great fun to go out with but, more importantly, I value our closeness.
"We have busy schedules but no matter where either of us are in the world, we know we can just pick up the phone and unload on each other, and that we are always ready to listen or offer advice.
"If you have two or three friends like that in this world then you can call yourself blessed. She is very special to me."
Cara, 24, loved working with Rihanna on their new movie and recently shared a story about the singer which she feels sums up Rihanna completely.
She said: "I've seen her work in the studio, in concert, in meetings. But to see her act was incredible. There was a moment where 'Valerian' director Luc Besson was trying to make her cry, to be emotional. He was like, 'Imagine that you get told that your song hasn't gone to number one and your performance is really bad.' I knew she wasn't going to give a s**t--that's not the way to get into her emotion. And she literally said, 'You're kidding me? I couldn't care less'."