The Irish-born actress joined "GMA" earlier today and opened up about her role in the hit film.
"I was a huge fan of [Gerwig] anyway, even before I met her and she's incredible," Ronan said.
"[Gerwig] really knew what type of filmmaker she wanted to be and it was a very natural position for her to be in and to watch someone come into their own and do something they were born to do is amazing," Ronan gushed.
While the film focuses on Ronan's complicated relationship with her on-screen mother, played by Laurie Metcalf, the young actress said she's on good terms with her parents.
"I have a fantastic relationship with my mom. She's my best friend," Ronan said. "I was very, very close to my parents growing up. We were this little sort of unit," she said, adding that her mom "protected" her from becoming overexposed early on in her career.
"I felt like I was able to fully enjoy all of the positive things about working on a film set with brilliant filmmakers but was protected as well," Ronan said.