Alert issue

DiVojich,

Is this a classic team site or modern site of which type?  It sounds like it could be a permissions issue or weird settings issue since it effects 5 users.  You don't have require check out or anything enabled correct?  What happens if she creates a library alert, not specific to folder or file?  Does it work then?  If she is getting the alert sign up message, it usually should be working.  Have you tried subscribing the alert for one of these 5 users?  You mention full rights, meaning these 5 users have full control in the library?  Do all 5 users have this same duplicate user issue?  That's really where it sounds like the issue is.  Please provide more details on that.  Is one external and one internal?