Eh, the Council is a peace-time thing. When they need a war-time leader, Rick's back, no more voting.
That said, what should he have done? Bringing her back would have fractured the group, and likely forced her to be executed. She killed people, and admitted to it. Ty's not going to let that slide, and since the flu hit even WITH her taking that action, can't really argue that she even helped anything by killing the (isolated) people. If anything, she went into isolation to kill them, then went out to handle their water supply, she may have CAUSED some of the infection...
So yeah, best case, Ty doesn't beat her to death, and they're forced to have a trial. She did it, and admitted it. After causing huge divides in the group, she's either executed or banished (best case) anyway. And the group is messed up because of it.
This way, she's out without having to be killed, and got supplies and a head start. Rick can control the converstaion, and sell the punishment without the heat of the moment pushing for worse.
For now, Carol couldn't come back after doing that. Which has kinda been a theme this season.
Either way, anyone have a warm fuzzy that the prison is going to be around much longer? We're not going to be having council meetings for long, between the Governor being back, the fence failing, the flu wiping people out. We've got lots of disposable extras, pretty sure we're going to thin this herd back down a bit, and we'll get our dozen or so survivors out on the road again by spring...