“I said, ‘How do you do this?’” Ms. Murin recalled. “One thing she said really stuck with me: ‘There’s a little soul, just waiting, and that little soul is waiting for the right time.’”

Ms. McDonald also remembers the conversation. “I just let her know it’s going to be O.K. — if the role is going to be hers, it’s hers, and the same with the pregnancy,” she said. “I’d been through similar issues, and so she and I were able to commiserate.”

Ms. Murin went in to meet Ms. Levy — they knew each other only casually — and as soon as Ms. Levy asked how she’d been, she blurted out that she had just lost a pregnancy. Ms. Levy confided that she had had a similar experience.

“I said, ‘I’ve been there — I know what that is,’ and we just held each other’s hands,” Ms. Levy recalled. “And then we went in and read together.”

Ms. Levy’s own path to “Frozen” had also been complicated by her desire to be a mother. After a miscarriage, she had a difficult pregnancy in 2016, giving birth at 34 weeks to a three-pound boy by C-section. Six weeks later, she was in an audition room, belting out Elsa’s power ballad “Let It Go” for the Disney team. She didn’t get the role.

Ms. Levy, who is married to David Reiser, a professor of theater at Stockton University, focused on nurturing her son — Izaiah, now 2, and healthy — and began looking for other opportunities. But then Disney called again. A new director, Michael Grandage, was reopening the casting process. Ms. Levy returned to the audition room.

Mr. Grandage and Ms. Levy, who had never met, hit it off. “Caissie came in and offered a layer of humanity that I had never seen in the role,” he said.