Shields, 58, was a guest on "Live with Kelly and Mark" Thursday and explained the industry is different from when she was a model.
"The rules have changed since I was [a model]," Shields told co-hosts Kelly Ripa and Mark Consuelos.
She noted her daughter has done "little things here and there," and there is no stopping Grier from entering the scene.
"I fought it for so long," Shields said of her daughter's decision. "It’s such a different industry now than it was."
Elaborating on how the industry has changed, the "Pretty Baby" actress said, "We didn’t have social media when I was a model."
Shields said the modeling world has now turned into "a rat race."
Shields has been in Hollywood since before she could walk, appearing in her first commercial for Ivory soap at 11 months old. Although she mainly had print modeling jobs, she said she worried about her "ridiculously stunning" daughter being "interested in runway."
"That’s brutal, and backstage is just brutal," Shields said. "I never did runway. I don’t think I would’ve been able to handle it."
Eventually, the proud mother "had to give in" to Grier building a career for herself in the modeling world but had some rules for her.
"‘You are going to have a great work ethic, it’s not going to be comfortable and you’re going to listen to me. Those are my rules,'" Shields told Grier. She also added that Grier must attend college.
Shields' appearance on the show was to promote her documentary, "Pretty Baby: Brooke Shields," which premiered on Hulu in April.
In the documentary, Shields touched on being sexualized at a young age, her relationship with her mother, her rocky love life and how her daughters were not thrilled she made a tell-all documentary.
Shields shares Rowan Francis, 19, and Grier Hammond with husband Chris Henchy.