@Karyanne0 It sounds like they plan to scam Airbnb into refunding based on Covid. Assuming they booked before the end of May then if they can show Airbnb they have Covid I am afraid they will get a full refund. The giveaway is that they are claiming a flight cancellation as well which they wouldn't know about if they truly had Covid.
For future reference guests who ask for discounts do, according to many, turn out to be poor guests.