And it turns out she's been keeping it a secret for a while.
Matthew proposed to Kelly during a holiday to the Caribbean island of Anguilla on New Year's Eve with a ring designed to look like an earring belonging to Kelly's father, Ozzy Osbourne, and Kelly told Hello! 'I used to hold my finger up to his ear when I was little and say, 'I want a ring like that'. Now I have one!'
The couple began a long-distance relationship after meeting at the wedding of Kate Moss and Jamie Hince - who is in rock group The Kills with Matthew's sister Alison - in 2011.
The 29-year-old chef then made the 'biggest sacrifice' by moving from New York to Los Angeles so they could be together more often. 'Long-distance relationships often don't work out. We'd dated for a year and knew we wanted to be together. ' Kelly said. 'People say we're co-dependent but we just want to be together all the time. I've never felt this close to another human being, ever.'
Kelly also dismissed rumours Ozzy and Sharon would get a divorce (thank God). 'As if my mother would leave my father! They were never getting divorced, they were separated. Mum said, 'You're drinking again and I'm not going to talk to you', like any normal person would do. Then Dad got himself together. He's been under a lot of pressure - the new Black Sabbath album, my brother's MS ... Things can get too much for addicts to handle.'
Considering the upbringing and life that Kelly has had, that's one hell of a well screwed on head.