Miley Cyrus posted revealing shots of herself on Twitter wearing a Borat-style monokini aimed at promoting her new single "We Can't Stop"  that debuted on Monday, but sources say fiancé Liam Hemsworth thinks her recent behavior is "childish."

Miley Cyrus' new single, which made references to cocaine and ecstasy use, has shown a new, wilder side to the former Disney child star that Liam Hemsworth might not be too familiar with.

"He used to be obsessed with the way she would go wild. But it got more childish to him," a source close to Liam Hemsworth said, according to the Daily Mirror.

"He's growing up - and fast. At first they were yin and yang, balancing each other out. But they got more and more out of sync."

While Miley Cyrus and Liam Hemsworth are still engaged, they have postponed their wedding twice and haven't been talking, according to Us Weekly.

The 20-year-old's posting of her monokini photos aren't the only attempts at image rebranding that she's made.

Miley Cyrus has also been spotted wearing a "Sex, Drugs & Rap" Diamond Co. brand shirts while posting photos of her cleavage on Twitter.

"She was acting out. She felt somewhat neglected by Liam and wanted her presence known," the source close to Liam Hemsworth said, according to the Daily Mirror.

"Liam always admired Miley's independence, but this was more like a rebellion, and it freaked him out. She has undergone a complete personality change. She's basically thugged out. Liam originally loved Miley's wild side, but it began to grate on him."

Miley Cyrus' monokini photo will be featured as cover art for her new track.