The Real Story About Brooke Shields and Her Alcoholic Mom

Brook Shields on the cover of PEOPLE

By Liz McNeil

11/15/2014 AT 12:20 PM EST

Brooke Shields has been famous since she was 11 months old. From her first Ivory Soap commercial to her teen modeling to her controversial movies to her headline-grabbing romances, she's lived her entire life in the spotlight – just as her mother, Teri, a bus driver's daughter from New Jersey, wanted. "I was her greatest creation," Brooke 49, tells PEOPLE's Liz McNeil. "It was us against the world."

Brassy and bold, Teri was also a lifelong alcoholic, who, Broke says, "was never really sober." She earned notoriety as the ultimate stage mom, and was slammed for pushing her daughter into provocative turns in Pretty Baby, Blue Lagoon and the infamous Calvin Klein ad. "She never had a career plan for me," says Brooke. "It was just – more."

Now for the first time, the actress and model opens up about their complicated relationship in her new memoir There Was A Little Girl . She reveals how Teri could be emotionally cruel, criticizing Brooke as "fat," and still fiercely protective, picking her up from school ever day through high school. It wasn't until her death in 2012 "that I could fully understand her," says Brooke sitting barefoot and cross-legged in her Manhattan townhouse she shares with her husband Chris Henchy, 50, and their daughters, Rowan, 11 and Grier, 8. "And even though I understood her better than anyone, I'm not sure I ever will fully."

The writing, she says, "was the least cathartic thing I've ever done. I kind of went dark. I stayed in, drank more and ate Kits Kats for breakfast. I knew I needed to be uncensored." She reveals the extent to which her mom loomed over her romantic relationships and how she was sure Teri would know when she lost her virginity. Brooke hopes the book will allow people to see "the good the bad and all that love that was there."