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"It happened very, very quickly," she told BBC News. "He was dearly loved by his family."
Friends previously told how he was admitted to hospital near his home in Winchester, Hants, in recent weeks.
His condition deteriorated and it was understood that his cancer is so advanced that it is beyond treatment.
Dee, real name Cyril Nicholas Henty-Dodd, moved to Winchester 15 years ago and lived in a tiny, one bedroom flat.
At the height of his fame he compered Miss World, appeared on Juke Box Jury and Top of the Pops helped launch pirate pop station Radio Caroline.
Due to a disagreement between Dee and BBC bosses over Dee's huge salary demands, his contract was reviewed in 1969 and he left the channel.
He was offered £100,000 for a two-year contract with the independent channel LWT and commenced a series with them in January 1970.
But Dee fell out with the LWT management as well and they terminated his contract after only a few months. Dee lived in a tiny flat in Hyde, Winchester, and cut an anonymous figure, far removed from the star who was mobbed on the streets.
Earlier this summer, in his first interview for 20 years, he said: "Sadly, honesty and intelligence have vanished from national TV.
"Truth, interesting stimulating conversation, and, above all, real 'showbusiness' has been replaced by juvenile 'reality' shows and endless audition programmes.
"We need to remember what original entertainers and entertainment is all about.
"I've no regrets. If you change your past, you change your present. Bitterness destroys, but laughter lifts you.
"It's all been enlightening and as a girlfriend said the other day, 'you've still got your hair.'"
Dee was treated at the Royal Hampshire County Hospital in Winchester.