Talk:My Little Pony Equestria Girls: Mirror Magic/@comment-3410511-20170622060356/@comment-5837525-20170622205344

Metaphor. Magic is leaking out into the human world and causing trouble, so in a manner of speaking, it can be compared to a spreading disease.

The point I was making is that it's not something to be dealt with case-by-case. The girls can solve each incident as they arise, but unless they deal with it at the source, it's only a matter of time before the next incident -- which is the reason for Sunset's "whining", as you call it.