"The first thing she said was, 'Dada,' and then she'd call everybody else she loved 'Dada,'" Heigl says in the October issue of InStyle magazine of their daughter Nancy Leigh Mi-Eun (Naleigh). "She actually attached to Josh much faster."
The couple talked about adopting even before they were engaged, so when they adopted their baby girl a year later, the Life As We Know It actress says all her dreams came true.
But Heigl admits connecting with her 20-month-old daughter had its challenges.
"I had a lot of complicated emotions about it because I chose to go back to work," she says. "I love what I do and – this isn't just making excuses – if I weren't fulfilling this thing in me to perform, to live out my passion, I don't know that I would be the mom I need to be."
But Heigl, who now only works three months a year instead of nine, says the mother-daughter relationship between her and Naleigh has improved since wrapping Life.
"Naleigh learned with me that the word 'Mama' was synonymous with kisses," Heigl says. "So when she first started saying, 'Mama,' she would also make a little kiss sound ... She started saying it maybe a month or two ago. I would come into the room and she'd go, 'Mama!' And it was like, Thank God."
For more from Heigl's interview, pickup the October issue of InStyle, on newsstands Friday