Yep, that one is safe. It's not possible for it to have caused the computer to crash, so something else is going on with your system.
I would recommend for you to scan you system for malware or a virus with Malwarebytes
and ESET Online Scanner
to help be safe.
As a test, create another new standard or administrator account for your wife to see if you are able to change the desktop backgroup while logged in it. The other account may have been corrupted.
Hope this helps,