The Poison frontman was appearing in US show Celebrity Apprentice with the TV star before he was taken to hospital after suffering a brain haemorrhage.
"I have known Bret for 30 years, Bret is a good friend of mine - I am completely devastated by what has happened to him right now," Sharon told Entertainment Tonight.
She added: "It is just hideous. It makes you feel all these different feelings. Your heart goes out to his family. Your heart goes out to him. He is the nicest guy in the world.
"Then you start thinking of your own mortality. It makes you appreciate how lucky we all are."