Sounds like this is working as intended…
- Your moderator is watching the category.
- This means that she is automatically watching every new topic in that category.
- Notifications are generated for every action in a watched topic, including edits… Such as editing tags.
This moderator probably also has “activity emails” (second option under preferences>emails) set to “always.” There has been some discussion on improving the copy for that setting, as it does include activity from watched topics. See