Former Bond girl Fullerton claimed that Reid lacked charm and had expected to win the competition in her column for The Telegraph.
Fullerton - who was the seventh celebrity to be voted out this year - explained that she felt Reid had alienated other contestants with her "PR campaign".
She wrote: "All those votes from Grimsby couldn't save Susanna Reid, who approached this competition with a PR campaign driven with military precision.
"There was definitely an Obama-style use of social media and a lack of charm that left most of us bewildered.
"Every time she entered Tess [Daly]'s room there were uncomfortable mutterings. It seemed she'd convinced the media she was the outright winner."
However, Fullerton was more supportive of Reid's fellow finalists. Speaking about fourth-placed Sophie Ellis-Bextor, she said: "We all felt it was unjust as she should have been in the final three, giving the audience the chance to see her sublime Charleston one more time. (Thank goodness for YouTube.)"
On Natalie Gumede, she wrote: "If it was a contest for the best dancer, she would have won, easily, but I know she will have a glittering career."
Finally, on the show's eventual winner Abbey Clancy, Fullerton stated: "[Abbey is] the most gorgeous, deserving winner of Strictly ever.
"I watched this girl go from nervous, pre-judged, non-dancer to the belle of the ball, the nation's new sweetheart, a charismatic dancer with bucket loads of charm and personality.
"She is totally natural but it is her work ethic and drive that impressed. Abbey Clancy danced into our lives and I have a feeling she won't be dancing out any time soon."
An average audience of 11.5 million tuned in to watch the final of Strictly Come Dancing on Saturday (December 21).
Watch Abbey Clancy and Aljaz Skorjanec's Showdance on Strictly Come Dancing below: