The 27-year-old actress is believed to have just got engaged to her 'The Rum Diary' co-star and friends say she's the woman who has finally tamed him, reported People magazine.
"Amber has called the shots since day one, dictating when they went public, for example. She's half his age and that's part of why he'll do whatever she wants in order to keep her," a source said.
"He has definitely toned down his behaviour since he started dating Amber. He acts like a mature and charming man now."
"Amber is a female version of Johnny. She's sort of kooky and outspoken, and while that would intimidate many guys, it is a turn on for Johnny," the source said.