Before the Governor enters the room to interrogate Maggie, she is shown from behind, wearing a racerback tanktop with bare shoulderblades. After the Governor enters the room, she is shown from behind again, except now she is wearing a bra with regular straps under the racerback.
Michonne tells Rick she knew where the prison was because Glenn and Maggie mentioned the direction to the prison and that it was a "straight shot". However Glenn and Maggie never even knew Michonne there and never mentioned the prison's location. All she heard was that they were living at the prison. The fact Michonne found the prison isn't hard to imagine, its location would be printed on any local map and/or road signs could have directed her there.
When the group are outside the Governor's town and watching the sentries, the first sentry's rifle barrel is bent.