Lizzie Purbrick, who competed as a showjumper in the 1980 Games, said she had used a key to get into the south London home of former lover David Prior.
The two, both separated from their married partners, had been in a relationship for several years that she had thought “had longevity”, according to her lawyer Simon Nicholls.
But when the 63-year-old saw Lord Prior in the arms of another woman (who was herself married to another member of the House of Lords), she sought revenge, Camberwell Magistrates’ Court heard.
On 9 May, she used a key to get into the home and used a garden sprayer and several litres of pig’s blood to cover the walls with phrases, including “whore”, “lady s***” and “big d*** lord”.
The court heard that she had chosen pig’s blood because Lord Prior “liked pigs”.
Purbrick, of King’s Lynn in Norfolk, also drew a penis on the floor and left a cheque for £1000 before leaving.
Her handiwork was discovered when a neighbour noticed blood seeping through from underneath the door.
When she appeared at court on Tuesday, she admitted one charge of criminal damage.
Mr Nicholls said: “This whole case has the feel of something lifted straight out of the pages of a Jilly Cooper novel.”
However, Mr Nicholls said his client had described the incident as “cathartic” and had since “moved on”.
She had also handed herself in to police following the incident.
Lord Prior, son of former Conservative cabinet minister Jim Prior, was MP for North Norfolk from 1997 to 2001 and chairman of the Care Quality Commission from 2013 until 2015.
District judge Susan Green sentenced Purbrick to 120 hours community service and imposed a restraining order, describing the slogans in the home as “highly abusive” and “quite appalling”.
After the hearing, Purbrick said she was “relieved not to go to prison”, adding that the judge had been “very nice” and a “sweetheart”.
She said she had to catch a flight to South Africa to stay with family but, when asked what that would mean for her community service, she said: “I think I’ve got two years to do 20 hours – I didn’t listen to be honest.”