What most naturally follows?

How to respond to a rude person
Choose whether to respond.
Not everyone who is rude to you deserves a response. If she is clearly trying to drag you into a fight by being nasty, don't let yourself be pulled into a battle that serves no purpose.
Resist the impulse to defend yourself in the moment, which ends up being a more powerful way of protecting yourself. This may be easier with an acquaintance than a co-worker or family member, but you still have the right to ignore someone who is being rude to you.