Negga and Cooper have been together for six years and currently feature in the TV show "Preacher".
"It can be so lonely filming, so it's like your buddy and your back up.
"He's got my back and I've got his. Very much so," the 36-year-old actor told Harper's Bazaar Magazine.
Negga said she having a "buddy" such as Cooper who keeps an eye out for her is a good feeling.