Kelly appeared on Sharon's US show The Talk and said her mother inspires her more than anybody else.
The 26–year-old said: 'People automatically assume that once you're in the public eye, everything's amazing and your life has always been amazing because you're in Hollywood, but you know, my mum has had the hardest life you could ever imagine.'
Osbourne thinks Sharon, 58, is a hero after battling colon cancer.
She added: '[Going through a family member's cancer makes] you realise that at the end of the day, all you have is your family.'