Tricky situation for you, @Brenn0, that doesn't give you much of a leg to stand on. Third-party bookings are not allowed. He should have booked for himself, and then said no to paying anything to her outside the platform. Asking for a cash security deposit is not allowed either. When she asked, he could have reported it to Airbnb (if he had booked for himself) and then been rehoused. Instead he paid it and made everything worse.
Did he wreck the place? The fact that she has got him out, kept the deposit, and blocked you, might mean that all did not go well. Your friend has done nothing good for your profile. I would be giving him an earful.