@greentext this is actually VERY simple.
Realize that the "bloat" come from all the windows updates. When windows was "new" it ran fine on these older machines.
So you just refresh windows with factory settings, and turn off windows updates, and tell the Karen to NEVER update windows because the updates are what's slowing her computer down.
If she's worried about viruses, there are anti-virus programs that will cause less issues that the fucking windows updates.