Michelle Williams broke down when a video montage featuring her ex fiancée, Heath Ledger and their 2-year-old daughter was shown at his memorial service last week.

A U.S. publications reports that the tribute – which was played during the Brokeback Mountain stars funeral in his hometown of Perth, Australia last week – was complemented by Ben Harper’s song Happy Ever After in Your Eyes – which was specifically written for Matilda at Ledger’s request.

"Just seeing it all there in front of you was humbling," a mourner told Us magazine. "It's just amazing how much he fit into his short life.

Williams, who returned to work on the New York set of her new film Mammoth earlier this week, is said to be keeping strong for the sake of her daughter.

”She is really keeping it together," the source continues. "And she's so great with Matilda."

The insider concludes that the former Dawsons Creek star is "still very heartbroken" over the Oscar nominee’s untimely death, but "she is happy to be working," because "It is a welcome distraction."