Rick can be blamed, Glenn and Daryl wanted to go look for her but Rick said no. Tyrese and sasha also reported her to the Governor for jumping the wall, causing him to chase after her

 

Didn't the governor already know? Milton told him before hand that Andrea was planning on going to the prison, and the gov told him to help her. He had his plans set up already.

 

That was the first time when he let her go to the prison. The 2nd time after Tyreese told him he chased her down. He didn't want her telling the prison group about his plan to kill them all when they gave over Michonne.