Left Shift Key Makes Everything Disappear; Right Shift Key Works Normally

My 85-year-old mother (and Wall Street exec) is in a panic. She has an iMac she purchased two years ago; she is on Sonoma 14.6.1. She was working on a business letter and "suddenly" all her desktop files shifted to the right; she cannot drag them back to where she had them. Her computer also generated folders for her documents all on its own. The most problematic issue is that when she clicks the left shift button, everything onscreen disappears. It returns when she clicks the left shuft key again.

We have tried restarting the computer, restarting holding down shift-control-option. We have gone into System Settings -> Keyboard and have hit Restore Defaults on everything. Nothing changes. What else can we do? Please keep in mind she is not computer savvy. She did not even know she had a power button until a few minutes ago.. She was unplugging and replugging her power cable. And she had no idea she could create folders to store her docs. So any solution must be easy for her to follow. Thank you.