At 21:00 a boom operator is clearly visible running down the road.
When Rick's group disrupts the staged fight between Merle and Daryl, Maggie easily takes out a walker with a head shot and then dispatches Haley. Just as Rick throws out the tear gas canister, the Governor can be seen standing all by himself at right center when the camera pulls back. Given that Maggie knows who the Governor is, there is no reason why she could not have killed him then and there, which would have greatly diminished, if not pretty much ended, the threat posed by Woodbury. to the prison.