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.
While on "Popcorn" to promote her new Netflix show, "Julie's Greenroom," she spoke about the possibility of a film remake or retelling of "The Sound of Music," another classic that earned Andrews an Oscar nod.
"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."
Check back later in the month for the full interview with Andrews on "Popcorn With Peter Travers."