@Nanxing0 "If a property is found to be bed bug infested, their policy is to suspend the listing for 3 weeks and then you need to provide proof of bug free (like a K9 inspection report) to be able to host again. "
I think you're wrong. It isn't if a property is "found to be infested"- they suspend the listing immediately according to all reports here, then the onus is on the host to hire a exterminator and submit the report- that either no bugs were found, or the property was treated.
@Junni0 This definitely sounds like the typical lying, scammer guest. Since she's probably already in touch with Airbnb, I guess you could either contact Airbnb to say this guest is scamming to get a refund, as you have guests there now who have had no such problem, and they surely would if it were true, or wait to see what happens.
Airbnb is so hard to get a response from now, that might work in your favor- if she can't get ahold of them easily, maybe she'll just give up the refund idea.
Good luck.