Agreed, the way they are writing Lori's character is bizarre and/or downright sloppy because he behavior doesn't match the circumstances nor what she's asked Rick to do related to Shane.
Outside of that it was a great episode.
Lori definitely isn't my favorite
character, but for the most part I think she's been written pretty well on the show. It's only natural that someone would have such conflicting emotions in her situation, and even though part of her realizes Shane was a threat, there's still a good chance he WAS the father of her baby.
And much like with Rick, her anger seemed more a reaction to the fact it had to be done at ALL, given how all three used to be such good friends.
Plus, sometimes people just get angry and act in strange, irrational ways. Or lash out for no reason. Especially when it's the end of the freakin world. I hardly expect everyone to be charming and likeable in that situation, and find it strange that somehow fans expect that she should be.