One thought on Lori...
Apparently Kirkman has suggested that Lori's reaction was that she was angry with herself. That does not match what we saw on screen...but that COULD be a plausible reaction. After all, Lori knows something that Rick does not...Lori's final conversation is what set Shane off.
Lori caused Shane to snap. If you watch the episode, prior to that conversation, Shane seemed almost resigned to his fate and the fact that Rick was in charge. He could see that he was slowly being replaced and that his behavior was making him more of an outsider. As he said to Lori...he did not expect any help.
Then Lori opened her big mouth and Shane snapped. If Lori had kept her mouth shut, Shane would still be alive. But instead she pushed him to the breaking point. Right after that he decides to kill Randall and then Rick. Lori has to know that's what happened and that might explain her odd behavior. How does she tell Rick that he own actions probably caused his best friend to try and kill him.