And the buzzing is definitely not just in the ears ? ( )
Of course the buzzing is in her ears, how else would she hear it.
Can I suggest you check the pins in the plug to make sure none of them are faulty.
Also, as you had a different keyboard which possibly had a volume control built-in, try removing the the keyboard from within "Device Manager" then re-boot the PC. "Removing the keyboard should not stop you from being able to re-boot the PC" when it will then re-install the drivers again.