The 44-year-old star, who has no kids herself, said she found it "strange" to quickly develop a strong maternal bond with her on-screen children Noah Scnapp and Charlie Heaton, reported Female First.
"Honestly, I felt like Noah and Charlie were my kids. It was a bit alarming - it happened in an instant, almost like when my niece and nephew were born.
"It was like for the first time in my life I understood how you would jump in front of a bus for this little baby that you don't even know yet. I did feel Charlie helped me a great deal with the emotion. He's a tremendous actor," she said.
"These kids are so incredible and special and talented, and they all love doing what they do.
"The only thing I could sort of say to them is that getting to do the work is the reward, that life is short and you have to enjoy what you do - and we really, truly did," she added.