@Chloe275
It's clear in your listing there is a cat. In the rules that must be acknowledged before booking -
Pet(s) live on property — We have a cat called Arnie.
Plus picture number two has Arnie on the balcony.
Probably you could have written a public response to the review to defuse, although it's passed the deadline now.
Going forward, I think you have enough good reviews in the bank that most reasonable potential future guests will overlook the cat review or it will not be so prominent as new reviews supersede it.
You overall rating is 4.83 so one cranky score won't have much impact, don't dwell on it, it's just an occupational hazard as is the odd malcontented guest.
Have a word with Arnie about his shedding though.