Sophie Tucker, 23, from Devon, admitted making up the allegation that he forced her into a sex act after the fiance saw his boss leaving her home.
Police later found intimate photos and messages she had sent to the man.
Tucker was ordered to attend a thinking skills course, by the judge at  Exeter Crown Court.
Judge Ian Lawrie called her "selfish and cowardly".
The court heard she had invited the 50-year old to her home.
The man spent almost seven hours in custody and had to submit to having samples taken by a nurse.
The court was told his business suffered.
Judge Lawrie told Tucker: "You must have known what you were doing was going to make life very difficult for [the victim].
"You showed selfishness and cowardice which are deeply unappealing."
She said: "I am thoroughly sorry about what I did and if I could do something to help him I would.
"It was a stupid thing to do. He has not done nothing. I wish I could undo it."
A woman who falsely accused her fiance's boss of a sex attack was given an 18-month suspended sentence for perverting the course of justice.