Natalie Portman found herself with just two weeks to prepare for her difficult role in the TIFF movie Love and Other Impossible Pursuits, after original actress Jennifer Lopez dropped out.

The comedic drama about the complicated personal life of a young, married New York woman -- who's grieving the loss of a baby while dealing with a difficult stepson -- would have been quite different with Lopez as the lead.

"That's always the way it is in Hollywood: The next move, if JLo can't do it, is to get NaPo," director-screenwriter Don Roos cracked yesterday, sitting beside Portman during roundtable interviews yesterday.

"We went to NaPo and we weren't sorry."

Added Portman, 28, with a giggle: "Anyway, it was kind of awesome 'cause all through filming Don would be like, 'JLo would have done that much, much better.' "

Turns out that Portman -- who flew into Toronto straight from Belfast, where she's shooting the medieval comedy Your Highness opposite Danny McBride and James Franco -- had way more in common with the lead character, Amelia.

"It was amended for Jennifer, really," Roos said of the script, which he based on Ayelet Waldman's bestseller of the same name.

"The book is written figuratively for Natalie Portman. The same age, the same background, a New York Jewish girl. It's just exactly what you would think of Natalie, but we bent it in a different way for Jennifer, and we just had to unbend it -- and it was just a delight to actually go back."

Portman, who doesn't have any children and isn't married, said she has known women who have lost children and has observed the impact the tragedy has had on them.

"I mean it's horrific, but it's an interesting thing to see how people deal with the difficult things life throws at them," she said. "I've definitely known people who don't want to have children, because that's just your fear from the moment you have a kid. I know it with my dog. I have nightmares every night. And I can only imagine it's a hundred times worse (with a child)."

She also liked Roos' take on the often unlikable character of Amelia, who has a sarcastic sense of humour that she uses as a defence.

"(Producer) Mark Platt was like, 'Listen, I promise you that Don will be uncompromising. He's not going to make her cute, he will definitely allow her to be as difficult as she reads on the page.' "

Portman, who made a striking film debut in 1994 as a child assassin-in-training in The Professional, said the role of Amelia also continues to show audiences that she's actually a grown-up, something she established with an Oscar nomination and Golden Globe win for her work as a stripper in 2004's Closer.

"It's weird 'cause I feel like people don't necessarily think of me as a woman yet, but I'm almost 30 now. I'm like, 28 ... I'm closer to 30 than 20. And I'm like, 'Oh, my God!' And so you want to be reflecting things more that are expressions of womanhood, as opposed to little girlness."

When a reporter suggests that that's something that can wait until she's 40, Portman shrugs.

"You never know. By the time I'm 40 I think people will probably be sick of me. They'll be like, 'Thirty years of this s---! Enough!' "

Portman, who has dated some equally famous men while growing up in the public eye, also agreed that love continues to be an impossible pursuit for her.

"Yes!" she said, laughing.

"It's going to happen," Roos said. "She's a nice Jewish girl. There's a doctor and a dentist, a therapist, a lawyer out there for you ... You will find him."