I am building a mobile app to allow for real time messaging, befriending users, creating groups to both chat and share images with, as well as creating events that users can invite one another to.
In researching I came across Firebase, and while there are major benefits, it perhaps may be overkill for my application and it appears it is for real-time collaboration, ie. pair programming, real-time massively multi-player gaming and related.
For the app I defined is Firebase overkill?
I think that seems like a perfect example of an app that would use firebase. I don't think it's overkill at all. If you want to build a simple app that has real-time functionality, firebase is the perfect solution.
That said, images can be tricky in firebase right now (since you'll probably want to use some other cloud storage, here is the stack overflow that discusses this: How to store and view images on firebase?), but I still think it's the right option for what you have described.
