The pop singer has written some comedy vows for the ceremony which will celebrate her new-found friendship with the Simple Life star.
One of Britney’s lines apparently contains a thinly-veiled jibe at estranged husband Kevin Federline: “We don’t need men to take away our pay cheques and self-respect.”
A source told the Daily Star: “They have been inseparable since Brit’s split. So their chums have started calling Paris her new husband. Paris has even been playing daddy with Britney’s kids. The birthday bash is a celebration of their new friendship and Brit’s impending divorce. They share everything.”