Sullivan said that Gaga started out as a shy brunette who loved piano ballads, but changed herself to please boyfriend, drummer and bar manager Luc Carl, the Mirror reported.
The book reveals that Gaga made a heavy metal song to impress Carl.
Sullivan also claims that she wrote Paparazzi about Carl, because she used to call him Papa.
The pop singer dyed her hair blonde so she could sign to a major label and that all her friends said she'd 'sold out', but Carl 'loved' her blonde hair.
The book reveals that when Gaga dumped him, she told him, "One day you're not going to be able to get a coffee in a f--king deli without seeing or hearing about me."