Andrews, who won an Oscar in 1965 for playing Mary Poppins, said the new film, "Mary Poppins Returns," set for release next year, isn't a remake.
"Disney had so many of the Mary Poppins books in their stockpile, in the basement, in the vault. So they thought, 'Why don't we also do a second musical using all of that material?'" she said on "ABC's "Popcorn With Peter Travers." "It's not a re-creation of the original film. It's a brand new film."
She also told Travers it's a "different era and time."
Andrews, 81, has not seen the new movie, but she has a lot of faith in Blunt.
"I think she'll be practically perfect," Andrews said.
"It's not so bad if they do," she said. "'Sound of Music' was iconic, and I'm thrilled it stood up to the test of time, but it was something like 50 years ago. So I think it's about time somebody had a crack at it again."