Busy Philipps ''can't believe'' it's been 10 years since the death of Heath Ledger.

The 38-year-old actress is close friends with the late actor's former girlfriend Michelle Williams - with whom he has daughter Matilda, now 12 - and has said she is still struggling to come to terms with the death of the 'Dark Knight' actor, who passed away in January 2008 from an accidental drug overdose at the age of 28.

Busy said: ''That anniversary, just brought up a lot of ... I can't believe it's been 10 years. I was pregnant with Birdie. I had seen him a couple months earlier, and you know, [Williams and Ledger] were broken up. I've never talked about it. I've never shared it, because I'm hyper protective of [Williams] and her daughter. But I also think ... I think it's OK. Everyone's allowed to have their own feelings about something that happens.''

The 'Dawson's Creek' alum - who has nine-year-old daughter Birdie and four-year-old daughter Cricket with her husband Marc Silverstein - posted a tribute to Heath on the anniversary of his death, and was accused by some of being exploitative of her best friend's sorrow.

Speaking about the criticism, Busy told The Cut: ''I think some people felt like I was being exploitative. I've never even really spoken about [Ledger's death], because I never would want to have it be misconstrued in that way, but it was the 10-year anniversary, and ... It's just been a long 10 years, you know?''

Meanwhile, Naomi Watts - who previously dated Heath from 2002 to 2004, before he began his romance with Michelle - recently took to Instagram to post a tribute the 'Brokeback Mountain' star on what would have been his 38th birthday.

She wrote: ''Happy birthday to this darling heart. We will never forget you... #heathledger #rip (sic)''

Naomi - who has Alexander, 10, and Samuel, nine, with her ex-husband Liev Schreiber - also previously took to social media to mourn her former beau on the anniversary of his passing.

She posted: ''Thinking about this beautiful soul today. 10 years ago he left this world. He was a true original. Heart always on his sleeve, with the most powerful charisma, strength, humor and talent. I will never forget his gentle spirit. (sic)''