Speaking to OK magazine, the 30-year-old one-time Dawson's Creek star revealed how she struggled to work after the tragedy until she was asked to do Blue Valentine.
"You experience this terrible sense of loss and it was very hard to find some meaning to all of it," she said. "It was very hard for me to think about work anymore because I found myself cut off from the outside world.
"Making Blue Valentine restored my desire and enjoyment in acting again, that was the first time I felt like myself again.
"It helped me feel good again in a way that I hadn't felt like in several years. It rekindled my spirit in many ways."
She added that whatever direction her life goes in now, Matilda will always come first.
"Raising my daughter is my absolute priority and everything I do is to make Matilda's world as happy and secure as possible," she said. "Even when I'm working I still think about her and can't wait to get back to her at the end of the day. I hope one day she will see my movies and be proud of me."