The girl uploaded Sarabjit's photograph on Facebook and wrote about the alleged incident in a post, which went viral, with many slamming the guy.
Days later, a man, claiming to be an eyewitness in the case, said the girl fabricated the story.
Sonakshi says she feels embarrassed to have supported the girl earlier.
"Being a girl, gave the benefit of doubt to her, like many others! And like many others I am embarrassed and let down! Apologies to the guy. Admitting a mistake and apologising doesn't make anyone a smaller person... Thats what I've been taught!" Sonakshi tweeted.