The former Grey's Anatomy star, who's heading up her own new show State of Affairs on NBC this fall, talked about motherhood at an afterparty for the Television Critics Association press day at the Beverly Hilton on Sunday.
"With two children and a husband of almost seven years," the actress tells PEOPLE, "I feel like I'm finally a legitimate grown-up."
Heigl, 35, who left Grey's amid controversy in 2010, recently denied longstanding rumors that she was difficult to work with. But she admits her family – adopted daughters Naleigh, 5½, and Adalaide, 2, with husband Josh Kelley – have changed her for the better.
"I have a deeper understanding about what really matters and whose opinion really matters," says Heigl. "I'm not going to lie, I'm absolutely a neurotic actor," she adds. "But I'm less atwitter, and I'm less defensive, and I'm less afraid of what everybody thinks about me."
Family MattersHer relationship has helped, too. "I'll look at my husband and sometimes go, 'You know what? I'm doing all right.' Because if I was that big of an a------, he would not still be here," she says with a laugh. "He's way too cool to put up with that."
Now that she's returning to work after spending so much time at home, "I feel this horrible being-torn situation that I know all mothers feel." But Heigl says that won't stop her.
"I have a passion for my career, and I know that that is something that I sort of want to inspire my own daughters with in some weird way. I keep joking, it's either that, or this job will simply help pay for their therapy. I'm not sure which will happen."
Already, her work is inspiring someone special – her niece Madison.
"I just watched My Father the Hero with my 13-year-old niece," says Heigl of the film she starred in at age 14. "It was kind of awesome because she got to see her Auntie Katie at 14. [But] it was kind of a tragedy for me," jokes Heigl, "I like, peaked at 14."