To close out the story, my client followed my instructions for doing a completely clean reinstall of Windows 11, but clearly did not catch the "addendum" a gave her about the screen where you tell OOBE not to back up to OneDrive. However, she was able to promptly unlink OneDrive based on another bit of information I'd sent on how to do that.
I got a very charming email from her late last night that ended with: "So, I still had to do a clean install of Windows, but from there I was able to unlink OneDrive and after a couple of restarts, everything works great!
Thanks so much for all your help and research. I was at a total dead end before I reached out to you, and I wouldn't have figured it out without you."
At least she now has the result she wanted and can use the current latest version of the software she needs to use and doesn't have to wait for the next version to appear.