"I have my dad's genes, and my metabolism works so quickly," she says. "I have to really constantly eat."
Swank says that "P.S., I Love You," which opens Dec. 21, is "one of those movies, I think, that remind you of what life is about. The importance of not taking people for granted and that you don't know what's going to happen tomorrow, and the importance of friends. This movie is so much about how love is illuminating. I think Gerry just gave her such a gift in helping her rediscover herself through that love."
For a comedy newbie, Swank might have been expected to go for a lighthearted romp rather than a story with such tragic overtones. It did present certain challenges, Swank says.
"It's not your obvious comedy. So it is finding the balance of the comedy that is based in reality, and the flip side of those emotions -- to be honest [about] the grieving and the anger and the loss you feel when someone dies. It was that fine line to walk back and forth."
Of course, working opposite Kathy Bates and the men in the film -- Butler as well as Harry Connick Jr. and Jeffrey Dean Morgan as the new men in her life -- certainly made her work a bit easier. "Such a great trio of guys," she says with a grin.
Especially Butler, whose turn as Gerry is engaging and sexy. "My feeling is that we don't go on this journey with Holly if you don't love Gerry and what our relationship was," Swank says. "It's only in the first 10 minutes of the film, but because you love him so much you can't believe he's gone too."
Seven months ago, Swank relocated to Los Angeles from New York after her divorce from actor Chad Lowe. She had first lived here as a teenager, but back then, she and her mother briefly lived in their car.
"My mom is an incredible woman," Swank says warmly. "We weren't in our car very long, but for me it was an adventure. I was in California meeting agents, so it wasn't in any way a downer."
Still, Swank, who will be playing doomed aviator Amelia Earhart in her next film, says she contemplates daily "where I am now from where I was growing up and how lucky I am."