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."

The pound hit $1.4693, a rise of more than three cents, or 2.34%, the biggest one-day gain since March 2009.
The bounce followed several polls over the weekend that suggested a very tight race, but that the Leave campaign may have lost a little momentum.
The FTSE 100 also rose, with shares closing 3% higher on Monday.
That is the biggest one-day gain since February.
Betfair, a firm that has taken in tens of millions of pounds in referendum-related bets, says the likelihood of a remain vote has risen from 65% on Friday to 72% on Monday.
"The pause in the campaign seems to have lent crucial support to team Remain," said Kathleen Brooks, research director at Gain Capital.
"The markets have always been more comfortable with the UK remaining in the European Union."
The pound had fallen sharply over the course of last week, after polls appeared to indicate the Leave campaign was taking the lead.
But figures from the Commodity Futures Trading Commission, a US markets regulator, suggested a broader change in trading sentiment by Friday.
That data indicated that by the end of last week, currency speculators had began to back the pound again by reducing their bets against the currency.
That contrasted strongly to the first week of June, during which time traders' bets against the pound had risen to the highest level in three years.
However, analysts say there is likely to be more volatility this week.
"Following the large sterling moves over last two days and limited risk premium priced in at this point, sterling now looks more vulnerable to negative surprise from the polls," ING strategist Petr Krpata said in a research note.
Monday's shift in sentiment has boosted shares in banks and builders, which are seen as more vulnerable to damage if the UK votes to leave the EU.
Shares in Royal Bank of Scotland and Lloyds Banking Group both rose more than 7%, while Barclays gained more than 6%.
Barratt and Taylor Wimpey, two of the UK's largest house builders, also saw their shares jump by nearly 7%.
Oil prices rose as well on Monday, with Brent crude trading up more than 2%, and currently hovering around the $50 a barrel mark, at $50.39.
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.
[NEXT_CONCEPT]
The pound has jumped the most against the dollar in seven years, as traders reassessed the likelihood of the UK leaving the European Union.