The former Coronation Street actress posted a photo of herself in the outfit before writing: "My Jean Paul Gaultier La Perla Dress... I wore to Zuma and China Whites."
After retweeting another image of herself with a fan from the same evening, she added: "They are just there... I didnt actually realise x (sic)
"I cant lie I'm really embarrassed about my boobs.. I just wear whatever dress I think is prettiest."
Flanagan then posted a self-taken photo at the Pennyhill Park Hotel, before adding: "Polo necks for me from now on... I'm actually sensitive x"
After being criticised by one follower who called her "dirty", Flanagan responded: "What do you think when you write a nasty message? Very Strange. Hating is bad for you x"
Earlier this month, Flanagan's exit from Coronation Street, where she played Rosie Webster, drew an audience of 9.28 million.
> In Pictures: Rosie turns model in Corrie
> POTD: 'Coronation Street' exit for Rosie Webster