The 26-year-old went to Las Vegas, where Sharon, 58, was filming America's Got Talent, to surprise her on the special day - and even managed to organise the tribute performance.
Speaking in her Closer magazine column this week, Kelly said: 'I flew with my mum to Las Vegas last week, as she was working on America's Got Talent, and I spent Saturday organising her Mother's Day surprises.
'I put up 300 balloons in her hotel room and got a Liza Minnelli impersonator to sing her a song during the break!'