Gaga presented Sharon Osbourne with a cake for her daughter as a peace offering backstage at the latest X Factor results show in London.
Kelly addressed the matter on Twitter tonight (October 27) by questioning why Gaga would publicly offer the birthday cake to Sharon and not deliver it to her in private.
"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 (sic)," Osbourne tweeted.
She went on to write: "You are so far behind you think you are first!... I live for a #Cause not for the #Applause!!!!!!!"
Kelly continued: "I like desert, but i prefer the truth… it's sweeter.. 'Let them eat cake' #MarieAntoinette."
Her tweets led to a reaction from Gaga, who wrote to her Twitter followers: "Monsters, please just focus on the positive of tonight's performance and do not send any hateful messages. I don't support it. #SpreadLove"
Kelly's mother Sharon had earlier tweeted: "Blown away by Lady Gaga's performance and graciousness."
X Factor viewers saw the 'Venus' singer hugging Sharon after the performance, with Gaga branding the judge a "goddess" and claiming they "got to hang out" during her surprise G-A-Y appearance last night.
The pair were also spotted by DS holding hands and posing for photos together once cameras went off as they had a conversation to clear the air.
They fell out when Kelly accused Gaga's fans of bullying her after receiving death threats from them on Twitter.
Gaga retaliated by writing an open letter to Kelly branding her a "hypocrite", saying that Fashion Police, which Kelly co-hosts in the US for E!, "breeds negativity" and makes people feel uncomfortable about their body image.
X Factor judge Sharon supported her daughter, writing a letter to Lady Gaga saying: "A word from you would stop all the hideous, negative and vile threats from your 'little monsters'. Let me know if you want to continue this debate."
Watch Lady Gaga perform 'Venus' at G-A-Y below:
The X Factor: Latest results show in pictures: