The photo shows Antoine wearing a belt that matched the one found near the body, The Star Phoenix reports.
Antoine also posted on Gargol's Facebook, writing 'Where are you? Haven't heard from you. Hope you made it home safe,' in an alleged attempt to cover her tracks.
Antoine initially told police that the pair had been out drinking on the eve of Gargol's death but that she had gone home with an unknown man at the end of the night and did not know what had happened to her friend.
However, police later received a tip-off that Antoine had made a drunken confession to the killing, CBC reports.
Antoine later admitted to the court that the pair had gotten into an argument, but that she does not remember killing Gargol.
She pleaded guilty to manslaughter and was sentenced to seven years in prison on Monday.
In a statement released through her legal representative, Antoine said: 'I will never forgive myself.
"Nothing I say or do will ever bring her back. I am very, very sorry...It shouldn't have ever happened."