Harmer, who is currently training for Strictly with pro partner Vincent Simone, said that she wouldn't let jibes about her size get her down.
"Hate on me as much as you like! But I like being curvy! #ShakeWhatYourMummaGaveYa," she wrote.
One fan said: "Too right and there's nothing of you, you're a size 6 to 8! Grrrrrr it makes me soooo mad."
Harmer replied: "Oh I know! No wonder there's so many girls that feel insecure!"
She told another supporter: "I know people are ridiculous! But I've never let it get to me and it won't start getting to me now!"
Harmer also revealed that she had a "lovely" training day with Simone, which featured an appearance from her younger sister Betsy.
She told Strictly co-star Lisa Riley that her only problem at the moment on the show was "being sexy". "It's not coming naturally!" she wrote.
Strictly starts on Friday, October 5 on BBC One.
[Strictly Celebs in Training - Photo Gallery]
Copyright: Twitter Denise Van Outen