Zellweger was said to have infuriated producers after opting out of piling on the pounds to play the hapless full-figured diary-keeper, as she did in the first two hit instalments.
Reports suggested the blonde had demanded the script was altered so the Brit character would have a smaller frame.
But a spokesperson for Zellweger insists there's no truth to the speculation.
Her rep tells GossipCop.com, "(The story is) so not true. Renee more than anyone would be true to the character."