The pair has been embroiled in a war of words since Osbourne was bullied by soMe of Gaga's devoted fans, prompting the Bad Romance singer to write an online note to her pal in January (13) criticising her role on U.S. series Fashion Police.
The row was further fuelled by Kelly's mother Sharon Osbourne, who lashed out at Gaga and branded her an "attention seeker".
The singer performed on the U.K. version of The X Factor on Sunday night (27Oct13), and received a standing ovation from Sharon, who sits as a judge on the show. The rock manager revealed they had sorted out their differences backstage.
Gaga presented a cake to Sharon in honour of her daughter, who celebrated her birthday on Sunday (27Oct13), but the reality Tv star has snubbed the peace offering in a series of angry tweets.
She writes, "Not to be ungrateful but why would you send me a birthday cake via my Mother in a country half the would away? #JustSendItToMe #LoveNotWar EatMyS**t #Hypocrisy.
"I like desert, but i prefer the truth... it's sweeter."