The 'Fashion Police' host has reached out to the 'Applause' hitmaker to apologise for acting ''like a child'' when the singer gave her mother Sharon Osbourne - who is a judge on the UK version of 'The X Factor' - a birthday cake to pass on to Kelly, who turned 29 on Sunday (27.10.13).
Gaga posed with Sharon and the cake after performing at London nightclub G-A-Y on Saturday (26.10.13) and though Kelly - who lives in Los Angeles - suggested the gesture was a ''publicity stunt'', she is now keen to move on.
In a post on her Twitter account, Kelly posted: ''@ladygaga I acted like a child last night. Just not into publicity stunts call me & we will end this like adults I dont want 2 fight anymore (sic)''
Gaga has not yet responded to the message.
Perhaps Kelly agreed to forgive and forget after Sharon - who hugged Gaga following her performance on 'The X Factor' on Sunday night - appeared to do the same.
Sharon tweeted on Sunday: ''Blown away by Lady Gaga's performance and graciousness.''
After hearing about the cake, Kelly flew into a rage posting a series of angry tweets which read: ''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
''#EatMyShit #Hypocrisy / #StefaniStopIt! / You are so far behind you think you are first! / I live for a #Cause not for the #Applause!!!!!!!
''I like desert, but i prefer the truth... it's sweeter / 'Let them eat cake' #MarieAntoinette (sic)''
The Osbournes have been locked in a bitter feud with Gaga for months, with Sharon branding the 'Alejandro' hitmaker - whose Born This Way Foundation campaigns against bullying - a ''publicity-seeking hypocrite'' for letting her fans send threatening messages to her daughter Kelly after she criticised Gaga's 2012 Grammy Awards outfit.
Sharon joined the feud after Kelly was inundated with abuse from Gaga's fans online.
Take a look back at October's inaugural event.
The film is expected to continue without Mendes' involvement.