'Charlie's Angels' ' Cheryl Ladd Plays Katherine Heigl's 'Deliciously Demented' Mom in 'Unforgettable'

"She's hardly warm and fuzzy," Cheryl Ladd tells PEOPLE

Cheryl Ladd played an Angel on TV, but in the new movie Unforgettable, she’s portraying a much less heavenly character.

“Helen is this grandmother nicknamed Lovey, which is incongruous because she’s hardly warm and fuzzy,” the former Charlie’s Angels star tells PEOPLE of her role in the new thriller. “She’s deliciously demented and a complete perfectionist. She was unlike anyone I’ve played before.”

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Ladd is a loving grandma in real life, but she had no problem finding inspiration to play the mom of Katherine Heigl’s character in the thriller.

“I’ve met people like this woman I play and they make the hair on the back of your neck stand up because they’re so calmly diabolical,” says Ladd, who recently launched Cheryl Ladd Signature Homes. “I imagined that my character’s mother was even worse and my character was warm and fuzzy compared to her mother — and it was a generational thing that’s being passed down, this perfectionism, this controlling mechanism.”

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As tumultuous as their on-camera relationship was, Ladd says working with Heigl was a joy.

“It was really interesting. Without any kind of major rehearsal or anything, we sat down and went through the scene and fell into this relationship,” she says. “It worked so great and off camera, we were doing Charlie’s Angels poses and having a good time. It was great. I loved working with her.”

Unforgettable also stars Rosario Dawson and is now in theaters.