although it’s very easy for a user to enable user alerts they sometimes don’t know how or where to disable or to delete them.
so how can we help them ?
Simple, go to the site from which the alert is originating, go to site settings > all site settings.
Look for: user alerts. open this option
this will route to a screen on which there are no alerts visisble, but don’t panic.
alerts are user bound, so first select the user in the pulldown (Display alerts for)
after you selected the user, all the alerts for that user for that site are displayed.
and now you can start deleting them.