@Kayla118 You should never cancel a reservation yourself (many of us only found this out by being readers of this forum) as Airbnb will punish you by blocking your calendar and "Host cancelled this reservation xx days before check-in" will appear on your review page, which of course can make future guests leery to book if they think they might get cancelled.
When a guest makes a booking that doesn't jive with your listing, or sends up red flags for you, always contact Airbnb, explain the situation, ask them to look at the message thread with the guest to see why, and ask that they make a "neutral" cancellation which won't block your calendar or penalize you in any way.
For this one, try contacting Airbnb CS and explain- hopefully you get an understanding rep who facilitates this easily and unblocks your calendar.