I can't really know for sure. If she hasn't been on the forums before I would boil it down to that but I can't be sure.
@Ilayne_Merespark is correct I did talk a bit about why @everyone shouldn't work, while I'm not sure why exactly it doesn't I wouldn't look to fix it because imagine everytime someone used it.
Literally, EVERYONE who has ever logged into the forums will get a notification EVERYTIME someone uses @everyone.
Looking at the uses of @everyone in the past week or so that is just too much and for not really any important reason that needs everyone's attention. If there was any reason for @everyone to work, it definitely would only be for moderators and staff for making announcements and such.