GG Leighton Meester "announces" engagement to BF.
According to multiple sources, Messter is ready to tie the knot with boyfriend Sebastian Stan.
The lovesick duo met on the set of the show last year where Stan played a recurring character.
The thesp has kept the news quiet but announced the engagement on her secret Facebook page, a source revealed.
Wonder what app Leighton used to clue her FB pals in?