Undermining Colleagues

It seems that no workplace is completely immune to the ill effects of gossip.  Our situation this time is no different.  Christine has not ever gotten along with her boss, and feels confident that she is smarter and more competent than him.  When given the chance to work off-site at an industry conference, she was excited to get the ear of her boss's immediate superior. 

Taking charge of this opportunity, she gave him a complete description of all that had gone wrong due to her boss's actions, starting with the facts, and injecting her outrage as she continued.  You are the superior in whom she confided.

What would you do?