Michelle Williams finds it hard to talk about Heath Ledger -- her former fiance with whom she has a daughter named Mathilda -- who tragically died early last year. "I didn't know what my boundaries were for a long time, which made interviews feel very unsafe. I can talk about grief, because that's mine; about single parenting; about trying to balance work and kids. But what I don't have to talk about is what happened between Heath and me in our relationship," she tells Vogue in the October issue. More Inside