BY BOB STRAUSS >Film Critic

Amanda Seyfried did not want to jump off that cliff.

"Everybody was scared," says the 22-year-old actress, referring to herself and co-stars Pierce Brosnan, Colin Firth and Stellan Skarsgard, who all play the possible father of Seyfried's bride-to-be in the screen version of the hit ABBA musical "Mamma Mia!"

They were all supposed to jump into the Aegean Sea from a rocky Greek island together for one of the film's montages. But as the carefully synchronized sunset shot neared, the "Mean Girls" and "Big Love" co-star could feel the apprehension grow.

"I was holding Colin's hand and Pierce's hand, and we all kind of stalled," Seyfried reports. "I thought, if Pierce isn't going, I'm not going. Then Colin felt me tense and he didn't go. And Stellan just flew off; he hated us, he called us all bad names."

The shot was eventually gotten, and Seyfried got to show off the singing and dancing talents that she developed as a child in Pennsylvania but hasn't displayed professionally since a teenage modeling career led her to acting.

Of course, "Mamma Mia!" raised that part of her game, too. Besides the three veteran actors, no less than Meryl Streep plays her movie mom, who isn't quite sure which of her former lovers hit the daddy jackpot.

Currently, Seyfried is putting in long nights shooting "Jennifer's Body," a teen horror comedy written by "Juno" Academy Award-winner Diablo Cody. Tough work, if maybe not as scary as jumping off a cliff.

But Seyfried seems to thrive on it - even when every fiber of her being screams not to.

"You know what was really challenging about `Mamma Mia!'?" she asks rhetorically. "Being on a beautiful Greek island, where all I wanted to do was hang out with my friends, and having to go to work. Which is something I normally love to do, but not there. They'd all be lounging around the pool and, like, `See ya later!' I was, `Nooo!' "

>Bob Strauss