The 'Gypsy' hitmaker presented Kelly's mum Sharon Osbourne with a birthday cake for her daughter - who turned 29 on October 27 - to put an end of their feud which began when the 'Fashion Police' presenter criticised Gaga's 2012 Grammy Awards outfit.
The bitter dispute escalated later this year when Sharon branded Gaga - whose Born This Way Foundation campaigns against bullying - a ''publicity-seeking hypocrite'', but the pair seemed willing to settle their differences posing for a picture together.
However, Kelly didn't appreciate the gesture and tweeted: ''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].''
The 29-year-old then followed it up by posting a picture of the cake and added: ''#EatMySh*t.''
Lady Gaga - real name Stefani Germanotta - was performing on the 'X Factor' yesterday (27.10.13) where Sharon is a judge on the celebrity panel and claimed it was a ''peace offering.''
The singer replied: ''I didn't know it was your B-day until this afternoon. Meant as a peace offering. Happy Birthday.''
after she commented on her outfit choice.