I don't have any experience doing this, so I could
definitely be wrong, but I've seen this scenario come up a few times, and I'm reminded of
this thread.
On the main title screen of ACNH, you should be able to press the (-) key, and talk to Tom Nook about removing another resident. My understanding is that usually, even when you are the resident representative, you can't delete another resident. However, I think there is an exception for when you have a resident who is not tied to a Switch account.
I would love to know if you have success or how you solve your issue. Good luck!