Sandra Brown has long believed her father murdered the 11-year-old, who went missing in Coatbridge in 1957.
The Crown Office has ruled Gartshore would likely have been indicted for the murder today had he not died in 2006.
They say there would have been a "reasonable prospect of conviction" if he had ever faced trial.
While Ms Brown admits the findings confirms her fears, she hopes the Crown Office review will help to bring closure to Moira's family.
"It's a really historic decision by the Crown Office," she said. "I feel that legal confirmation of a really terrible crime and the naming of a perpetrator is a huge leap forward.
"Her parents and sisters have never got over what occurred but I believe this will go some way in helping them come to terms with such unimaginable violence.
"I can't find the word for how I'm feeling, there are so many mixed emotions."
Gartshore had been considered as the prime suspect in Moira's death ever since she went missing in February 1957.
The schoolgirl sent on an errand by her grandmother, was last seen by two passengers boarding a bus driven by Gartshore.
And although he admitted to being the last person to see Moira alive, there remained a lack of evidence to indict Gartshore for her murder.
Ms Brown maintained her suspicions and believed her father had eventually left Moira's body in the open grave of an acquaintance, Sinclair Upton, at Old Monkland Cemetery, Coatbridge.
But when the grave was exhumed in January last year, there was no evidence the youngster had been there.
However, the Crown Office has now revealed a new key witness came forward and said she saw Gartshore dragging a young girl by the arms near to a bus terminus in Carnbroe.
Prosecutors said the witness had given a credible explanation for not coming forward earlier, and had not read any of the books or literature written on the disappearance of Moira.
Following the review, Ms Brown said: "Although it confirms my worst nightmares, it certainly gives me a sense that this will hopefully silence anyone who doubted my father was responsible."
Along with the testimony from its key witness, the Crown Office also said Gartshore had, during a conversation with relatives, admitted he was sexually attracted to young girls and, furthermore, attracted to Moira.
Another witness came forward stating the suspect exposed himself to her and Moira in a park in the summer of 1956, and he had known Moira by name when calling her over to him.
The Crown Office said: "The new evidence provides the sufficiency to allow Crown Counsel to take the decision that the suspect (Gartshore) would have been indicted had he still been alive.
"We reiterate that we are not saying the suspect is responsible for her murder - only that there is sufficient credible and reliable evidence to indict him and that there would be a reasonable prospect of a conviction, had he still been alive.
"We hope that this will provide closure to the family of Moira Anderson.
"There is no credible and reliable information as to the whereabouts of her remains."