Certainly an event is a project, but that doesn't necessarily mean that a project is an event. You could consider event management to be project management, but most project management has little to do with events (at least in terms of parties, celebrations, etc.).
The phrase "event management" tends to specifically refer to the handling of logisitics pertaining to preparing and hosting an event. The phrase "project management" tends to refer to the general principles of time, resource and schedule management.