The actress will reprise her role as Eve Lockhart in the new BBC One drama, which also stars Keith Allen.
"There's no mention of the older show or winks to it," she told TV Choice. "This is a new show and at no stage does Eve talk about what she was doing before."
She added that her character will be "in charge of a young team of geniuses" in The Body Farm.
"[Eve]'s certainly moved out of the lab and she runs the shop," explained the star. "There's a sense of family. Eve is slightly parental and we don't see them at home. Home appears to be the body farm."
Fitzgerald insisted that Lockhart will be the only Waking The Dead character to appear in the new show.
"Waking The Dead was created by Barbara Machin and owned by her," she explained. "My character... joined the show later, so we could use her."
She also admitted that some viewers were "really unhappy" when Waking The Dead ended in April.
"There was still a taste for it," she suggested. "I was sad not to be working with the guys, but at the same time I knew I had this [spinoff], so I was quite excited. I hadn't been in the show for a whole decade, like the others, so it was probably more painful for them."
The Body Farm begins on Tuesday, September 13 at 9pm on BBC One.
Watch the BBC's original drama trailer - including clips from The Body Farm - below: