She took a shine to the snap at Peach's exhibition dubbed One Night in a Melbourne Jail Cell because it makes her laugh.
"I bought it because Judith Collins looks ridiculous," du Plessis-Allan said. "I only had a couple of drinks that night so I can't even blame the booze. Barry wasn't with me but he told a mutual friend who was there to try to stop me from buying it."
Peach recently resigned from TV3 after a 10-year stint as a reporter. His debut exhibition in May was hailed a success and New Zealand's biggest private art collector Sir James Wallace even bought a piece.
Peach said the photograph of Collins, which the politician has described as being fun, was "about suppression and losing your power. Everyone is the same when their eyes are shut".
Herald on Sunday columnist du Plessis-Allan now intends to display the artwork at her Auckland flat.
"It is pretty big and I will have it framed and hang it above the bed," she said. "But when Barry is there I might have to flip it over to face the wall or put a sheet over it."