However, Emily - who welcomed her second child Violet with husband John Krasinski in July - is also working on some child-friendly movies, including the upcoming Mary Poppins remake.
She said: "Well, my girls can't see [The Girl on the Train] , can they?
"So I have to do a couple they can see. When I, hopefully, proved I'm not an unfit mother.
"I would have done Mary Poppins whether I had children or not, but the fact that I have girls makes it such a gift."
Meanwhile, Emily found it "liberating" to look less than perfect in The Girl on the Train.
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She said: "It was utterly liberating. Very often in films, the thing that will make you feel self-conscious as a woman is sometimes, if we're supposed to be playing a tough cop or something like that, yet you are still supposed to look pretty.
"It's something quite freeing when you're supposed to look like a wreck, when that overhead green lighting on the train is supposed to look awful on you."
- Bang! Showbiz