If cancer gets the best of King Charles, what happens to Camilla? Is she a "nobody' again? Where will she go?
Since she's Queen Consort rather than Queen Regnant she will cease to be Queen and Prince William will become King William, with his wife becoming Queen Catherine.
That said after the death of King George VI his wife Elizabeth was known as "Queen Elizabeth the Queen Mother". She was also Queen Consort and her daughter, the new Queen Elizabeth II, had taken the throne but she still had a role to play. Exactly what role Camilla has following Charles' death (assuming, of course, that he dies before she does) will largely be down to the wishes of Charles and William, with some consideration probably given to public opinion.