Let's be blunt: when there's a fire, the first thing that's required is to contain it. They failed at containing their public presence to a specific website/social network and now there are little flame wars sprouting everywhere and no way to adress every opinion.

Unfortunately, I believe the best option at this point for AirBnB is to do nothing about it for this specific case, and brace for the next impact by preparing the field in advance (centralize comments in order to assimilate and answer public questions).

This story should not be bigger than what's happened/happening to the victim - and that's huge enough already. Make her feel better first, then see what you can do about your "image". Tell your side of the story in one place and be receptive for critics. Something good can come out of this mess, but they won't find it if they think hiring more people to monitor/participate in more forums on the internet is a solution.