You are having lunch with three people you respect and admire. They all start criticizing a close friend of yours, not knowing she is your friend. The criticism is distasteful and unjustified.
I think the best way is to ask them why they are annoyed with your close friend? Then if you think that their reasons are unjust,tell them that it isnt appropriate and tell them she is your friend. I dont know,but if i know soMeone is saying bad thing about my friend,i will confront them and teach them oN how to earn soME manners.