Mrs Peterkin's problem could probably being solved by finding a way to precipitate the proteins of the cup of coffee, and centrifuging I guess the fat, while leaving the salt in suspension. One might then separate the salt by distilling the salted solution. The water can be recuperated and united again to the precipitate and the centrifuged fat.
Mrs Peterkin should address the problem to a competent person like PE without asking for a stupid advice to a woman from a town named like a cheese . If Mrs Peterkin had wanted to make a new cup of coffee, she would have made it herself in the first place!