There is a thin line between being a bitch to being a passive bitchive person. When a girl is a behaving as bitch to you, you know that you've been abused. It is easily identified. Passive bitchive behaviour is disguised by actions that seem to be innocent but are in fact a sophisticated way of expressing one bitchiness.
Passive bitchive behavior stems from the need to behave cruelly in an indirect way.
Liz the bitch: "you gained a bit of weight didn't you?!?!"
Passive Bitchive Liz: "I love it, it highlights your curves"
Fat Jane: "can you set me up with your friend?"
Liz the bitch: "You are way out of you're league hun..."
Passive Bitchive Liz: "Sure hun, hope he'll like you though"