How about Lori pulling Ricks strings to convince him to kill Shane. Dammm!
I'd say its reaching a point where there is no other choice for her. Shane at this point has completely lost it and his obsession over her can only lead to him trying to kill Rick.
Noticed we dont know a whole lot about the backgrounds of either Hershal or Dale. But until this episode. Neither has killed anyone or any walkers. Both have been hesitant to do so.
Hershals saying he "Knows how to shoot but doesnt like to." May be telling.
I'm thinking in Both Hershals and Dales cases maybe former Vietnam and Korea combat vets.
Any event In Hershals case I think with that statement he is suggesting that he has killed before. And not just sick horses either.