The story
From the implication that the speaker's dislike of the target is so intense that they could cause the speaker offense by performing almost any action. First attested in the 2010s.
Etymology from Wiktionary, CC BY-SA 4.0.
bitch eating crackers
Today it means: A person for whom one feels a strong and disproportionate dislike, to the extent that almost anything they do makes one angry or annoyed. Full definition →