I don't like her much either. How rude.

One strategy when people say mean or derogatory comments is to plaster a smile and say 'thanks' or 'thank you for sharing' & then going about your business. This typically throws them off, esp. if they see they can't get a rise out of you.

Trying to engage them or rationalise (e.g. explaining) will not work. Arguing or reacting also don't work as they will then become the 'victim'. As much as possible, ignore her / remove yourself from her presence.