Osbourne, 24, was among the 250 guests who attended the ceremony at the mansion of music mogul Irving Azoff.
"It was absolutely beautiful," Osbourne told Us Tuesday after taping Dancing With the Stars in L.A. "Lamar is the nicest guy, and I'm so happy for them. They are great together."
She has spent time with them and said they are "perfect for each other."
Osbourne even defended their decision to wed after just one month of dating.
"When you know, you know - and they know," Osbourne told Us. "When it's right for somebody, she can only know that. It's nobody else's business, just theirs. It was a fairytale wedding and completely beautiful."