“I can't find a meaning for it,” Williams told ABC's "Nightline." “I can find meanings in things and people and relationships that have sprung up [in the aftermath], and friendships that have strengthened. I can find a lot of meaning in that, but not in why.”
Williams and Ledger began dating after meeting on the set of the 2005 film “Brokeback Mountain.” They later had a daughter, five-year-old Matilda Rose but ended up separating in 2007, according to reports.
In the 12 months after Ledger’s death, the “Shutter Island” star began reading Joan Didion’s memoir “The Year of Magical Thinking,” in which the author talks of coping with her own husband’s death.
Williams said that first year was full of “very magical thinking.”
“It didn't seem unlikely to me that he could walk through a door or could appear behind a bush,” said Williams, 30.
The actress is getting a lot of buzz for her role in the upcoming film “Blue Valentine,” in which she plays opposite Ryan Gosling as a woman trying to save her marriage.
Later in the interview, Gosling joined in and lavished praise on his co-star.
“She's like Brigitte Bardot meets Clint Eastwood. She's like a sexy cowboy or something,” Gosling joked.
Since Ledger's death, Williams has been linked to film director Spike Jonze as well as to Gosling, although the stars denied they were romantically involved.
"We are 'doing it' creatively," Gosling quipped.
Williams is scheduled to appear in two films in 2011, including “My Week with Marilyn,” in which she plays 1950s bombshell Marilyn Monroe.
“Blue Valentine” opens Dec. 29.