The 29-year-old actress, who is dating Ashton Kutcher, is said to have piled on the pounds and has been stepping out in public looking less-than-polished, reported Showbizspy online.
"Since pairing with Ashton, she is constantly photographed looking like a total mess. It is not the image Dior wants to send. When they signed Mila, she was a total waif; they didn't worry about making her agree to a weight limit in the contract.
They are really regretting that now," the website said quoting a source.
"The company paid her a fortune and is very frustrated with how she looks. The marketing people have even offered to supply a wardrobe for her," it added.
Even her boyfriend Kutcher is reportedly not happy about her weight gain and has even dropped hints that she is 'fat'.
"Ashton has been with tons of models, and that is the body type he likes. He had been dropping subtle hints, but she was not getting it, so he just told her flat-out that she is too fat. They had a huge battle and Mila told him to leave if he has a problem with her weight," the source said.