The actress (25) played the role of strong-willed widow Lily Bell, who is killed off.
Lily Bell is strangled to death by unhinged character Swede (Christopher Heyerdahl) in the tense last episode.
Scripts were handed out just days before each shoot, so Lily's death must have come as a shock to the Irish actress.
"They gave us the script days before each shoot and there are pros and cons to that," Dominique said.
The petite blonde actress says she found working on the series the most challenging job she's ever done.
"When I was doing some of Lily's scenes, I found it so draining, emotionally, physically and mentally -- more so than any other shoot or character.
"I would go home with 42 mosquito bites, weighed down by 100lb clothes and corsets."
She added she spent a lot of time on set covered in fake blood, which must have prepared her for the gruesome finale which fans will see soon.
"Yeah, I was covered in blood and wounds and stuff a lot. I like playing strong characters," she told the Evening Herald.
The series currently airs on RTE2 on Friday nights at 9pm.