I think the "Karen" thing is just another hijack of the language .. meaningless, useless jargon and just a maladroit means to an end for those people who have no idea how to express themselves intelligently ... 
In the case of the poor lady re "eating babies" though, I'll stay with what I think: her thought patterns were scrambled.
Even if she was being sarcastic etc, it still presented her as someone mentally unbalanced to even stand there and do it.
