"It would have been nice if someone had contacted me," she said.
"It doesn't matter who it is acting in it -- it's just tasteless," Debra told People. "It's classless how everyone is rushing to release something for the 50th anniversary of this horrific event."
Debra, whose pregnant sister was killed by Charles Manson's cult followers in 1969, also called out a "fabricated" plot point she believes is in the movie: that Tate had a vision that she and Jay Sebring would be murdered.
"I know for a fact she did not have a premonition -- awake or in a dream -- that she and Jay would have their throat cut," she said. "I checked with all of her living friends. None of her friends had any knowledge of this. Tacky, tacky, tacky."
"It's total fabrication," Debra added. "It would have been nice if someone had contacted me," she said.
Duff revealed her role in the independent film "The Haunting of Sharon Tate" on Tuesday, with an Instagram photo showing her in costume as the title victim.
"Had the incredible opportunity of playing Sharon Tate the past two weeks in an independent movie," she captioned the photo. "She was an amazing woman and it was a true honor."
Sebring will be played by (Jonathan Bennett) in the movie.
Tat was eight and a half months pregnant with Roman Polanski's child when she was stabbed to death in their home on Cielo Drive in Los Angeles.
Manson died this last November at the age of 83, while serving nine consecutive life sentences in prison.