BEVERLY HILLS, CALIF. —  While Blake Lively’s character does not age past her late 20s in “The Age of Adaline,” the actress is glad her new film is a fantasy and that she — like the rest of us — will experience the process of growing old.

“Well, as long as it doesn’t happen too quickly,” said the former “Gossip Girl” star and new mom with a big laugh, as we chatted about her new movie at a Beverly Hills hotel recently.

Lively’s Adaline Bowman character stops aging after a car crash in 1934 alters her metabolism. The fear of being discovered as a human “freak” leads her to change identities approximately every five years.

“Since the beginning of time, people have been chasing the Fountain of Youth,” Lively said. “But in this film, here is someone who has found the Fountain of Youth, and we see it’s a terrible burden, a curse in fact.”

She sees the irony of making that point in Hollywood — a world obsessed with youth and beauty. In the real world, Lively believes, “The whole progression of life is right. You’re born, you live — hopefully a good, productive and wonderfully long life — and then you die. This is something I’ve recently thought about in a different way now that I’ve become a mother and contemplate my own daughter’s entry into our world.” Lively and husband Ryan Reynolds welcomed baby girl James in December.

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One intriguing twist in “The Age of Adaline” (opening Friday) is the casting of veteran actress Ellen Burstyn as Adaline’s daughter, Flemming — who, of course, ages normally. While her mom (born in 1908) remains looking like she’s 29 (when actually near the century mark), Flemming naturally is an old lady in the early 21st Century.

Lively said that working with the Oscar winner was a bit intimidating. “She’s so lovely, but she is much older than me and has such a regal bearing. She’s such an icon. I don’t have the life experience needed to act as her mother. That was among the biggest challenges in the film for me — to convincingly act motherly toward a woman so much older than me!”