@Beverly28
I think you probably need to step back a little - it doesn't really sound like a scam to me. If you were in her shoes and woke up with a rash - you might jump to the same conclusion.
I know this isn't helpful, but it's not an unreasonable conclusion for her to jump to.
I would consider it a scam if she left, saying nothing, and then contacted AirBnB to complain about bed buds and provided photos.
Having worked in the hotel industry and seeing one guest very distressed at being bitten by bed bugs I think I have some empathy for the woman if it was an honest mistake etc.
Good luck - and.....even if you don;t have them, they are carried by guests in their luggage and clothes. Get bed bug traps, which are very effective and put one under each bed. Check them and replace/refill them regularly - then if someone does complain you at least can say there are none other than what may have travelled with them!
Good luck