Carey – who split from boyfriend Shia LaBeouf earlier this year- said: “I was so happy when she came on to the film. We met playing sisters and we are like family to each other, so that bond was there to recreate on the film.
“Keira is the friend I call when I’m in trouble or suffering from a broken heart. She’ll meet me in the bar with a mojito and be there for me.”
Carey also insisted her friend is not as reserved as she is perceived to be.
She added: “She reserves herself for the people she cares about but when she comes to my birthday parties – and she’s never missed one since we met – she’s the first to get up and dance and the last to leave.”