@Cara230 This is a tough one, because both you and the guest have equally credible accounts of how the stay went, just with some minor discrepancies. It also doesn't help matters that you chose not to review the guest - this undermines the credibility of anything you might want to say in response.
Here's the reality check: it's only your 6th review, and while all the others were unanimously positive, it's a pretty small sample. Guests considering your listing will be comparing it with places with much more established reputations. They should recognize that you're still getting started and ironing out the kinks before they take a chance on a listing that's still in its opening phase. With that context in mind, it would be a very bad look if you tried to dispute the guest's detailed and qualified comments. The positioning of a drain lever that guests had no way to know about is not a hill you want to die on.
Instead, the best impression you can make on your prospective guests in the response is one of humility. For example:
"As new hosts, we are striving to create the perfect experience for our guests, and we appreciate the time you took to provide this feedback."
And then, list the improvements you have made since that review, to demonstrate to the next guests that you are on the case and ready to fix any problem that comes their way. You can inject a spoonful of shade to help the medicine go down: "Thank you for reminding me to inform our future guests to store their food safely to prevent visits from ants." The most important thing to keep in focus, as @Emiel1 said, is that you are not replying to A****y; your audience is guests considering your listing, and you want to show them your grace in the face of critique.