If you've seen the new promo, then you've seen Andrea standing over the Governor with a knife. She could just be trying to kill him (and is unlikely to succeed) OR she could be taking Michonne's place in a very iconic sequence. Obviously she can't cut his arm off with that thing, but the really painful thing she can do. Anybody else think Andrea will do this?
My theory is: The Governor sends Andrea to the prison (which kinda makes him look like a dumbass), Andrea stays for an episode or two and finds out about everything, she returns to Woodbury pretending like she got a lot of info and is still on his side, she sleeps with him, then after he's asleep, the chaos ensues.