She was an asshole who wanted me to redo work for free because she believed her son over someone who actually knew what they were doing, and after tens of minutes of wrangling I just went "fuck it" and obliged her request to sanitize the peripherals. The sum wasn't all that big to begin with, so it's not like she was on the hook for hundreds of euros – probably got a 50€ bill instead of a 20€ one. Not knowing any better obviously wasn't the problem here, but if that's your takeaway then I really don't know what to tell you.

So yes, I did it.
No, I'm not sorry.
Yes, I'd do it again.