The 'Price Tag' hitmaker - who attended the BRIT School in Croydon, South East England, with the singer - admitted despite both the girls being worldwide stars, they get back to their normal Roots whenever they see each other.
She said: "Adele and I used to hang out together at the BRIT School and sing together. I bumped into her recently and she was like, 'Baaaabe!'
"We're so common when we're together, it's hilarious."
While she can get back to her roots with the 'Someone Like You' hitmaker, Jessie - real name Jessica Cornish - claimed the only people she can hang out in her pyjamas with no make-up on is her family.
She added: "I'm able to be in my pyjamas and have no make-up on in front of my family - there aren't many people I can do that with any more.
"My sisters are like best mates and I can phone them and cry and say I've had a bad day and they don't judge me."