In Dannii: My Story, her new autobiography, Dannii recalls her first night on the UK version of the talent show when Sharon reportedly
"bowled in" and "demanded to know why I hadn't gone to the press to tell them what a nice person she was".
"The minute she left, I burst into tears," Dannii wrote.
"I'd managed to hold it together while Sharon had been there, but once she'd gone I couldn't hold it in, and I wept into my hands.
"Sharon was looming over me screaming and swearing... five minutes later she was holding my hand on stage. I wasn't crying because I thought there was any truth to what she'd said - I was crying because someone I had previously looked up to had bawled in my face and ruined my big night."
Kelly didn't waste a second, slamming the 38-year-old on Twitter to defend her famous mum.
"The best thing to happen to dannii's career was that my mother hated her," she Tweeted.
"She needs to shut her mouth and concentrate on motherhood!
"I will be the first one to admit that my mother did not play her cards right when came to dannii but trust me when I say Dannii is the devil. Dannii you are so lucky that I respect Simon enough to not tell the truth about what really happened. wa wa wa you poor middle aged victum (sic)."
Ouch! Sounds like there's something Dannii might not be telling us. Her book claims that her feud with Sharon lasted the whole series, with another judge, Louis Walsh, also taking Sharon's side.
Kelly had more to say: "Sorry I have just had to deal with this bulls**t 4 years and i have kept my mouth shut but i am sick and tired of her lies enough is enough.
"I think you all forget i was there i saw everything and if my mum was the "bully" why was she the one the left the show?
"To the 12 Dannii fans out there I ask you this question what would you do if someone wrote a book of lies about your mother?"