@Artistic-Haüs0 There is not an external body regulating Airbnb practices at this level or any organization that's concerned with whether small businesses receive the online reviews that their owners feel they deserve. It's just part of the cost of doing business that sometimes you're going to deal with a-holes.
If "Superhost" were a meaningful distinction, I'm sure your wife would be deserving of it, but I suggest you think of it more in terms of what Airbnb is actually using it for: to manipulate hosts into being subservient to their listing service. You and your wife decided that keeping your family and property safe was more important than 5-star reviews and stupid orange badges. In other words, you handled the situation like adults, and I'm sure you can also accept the consequences with aplomb.
Even so, if you prioritize quality guests and high ratings over maximum occupancy, your best bet is to decline guests like this in the future. According to your wife's review, the guest made "several attempts to negotiate down the rate on a late booking request." Of course hosts as experienced as you both know that this is a major red flag that you're going to have a problem guest and likely not come out with a perfect review. I know these are hard times and the near future for hosting looks quite bleak, but if you don't want to deal with problems like this again you're going to have to screen your guests.