The 27-year-old, who has been dating Mosshart for a year, recently made their romance public, reported Femalefirst.
"I wanted to give it time, I wanted to get to know my boyfriend before the world does. You can't keep something a secret forever," she said.
Kelly's brother Jack Osbourne recently revealed he has been diagnosed with multiple sclerosis and she says seeing him coping so well with the condition has helped her come to terms with his illness.
"What actually has made it better is waking up every day and seeing how amazing my brother is and how incredible he's doing. He has a brain that is very military-like. Where, even if he doesn't like something, he can make himself like it. And he's doing It just blows my mind!"
