Give the Revo Uninstaller a try..
I would suggest trying to uninstall it with the "Revo Uninstaller". The FREE version should do it. Have Revo remove anything Yontoo-related. There is no harm in trying it.
Depending on the browser your wife is using, you might want to first disable (or remove) any Yontoo Add-ons or Extensions.
Best of luck..