Ok, so this is what really happened. After not being satisfied with our offer to return up to 75% of our net if she cancelled, Marci told us her luck had changed and she could come after all. This was not true. To get all her money back she convinced her ex-husband to take the condo. She didn't tell us, she didn't tell him about the capacity limitations or upcharge for extra guests (to discourage more than 4). We learned this after our co-host told us there were again 5 in our condo and we wrote Marci again - who told us to contact Joe, who told us the truth.
So, as this conversation started, Marci sublet our condo to her ex-husband, who, claiming he was unaware of the capacity limit invited 1 more guest than appropriate into the condo for 10 or 11 days of a 28 day booking.
AirBnB was supposed to contact Marci and impose and upcharge, but AirBnB Support dropped off the planet and is not responsding to my emails. So, I sent Marci an reservation change request for the extra guest upcharge. Waiting to see what happens.
I assume Marci left a CC that is exposed to the charge if she declines. Has anybody else encountered a similar situation?