For as long as Twilight has owned her castle, she hardly ever has a need to take care of the entire thing. Most of the cleaning and such is handled by her and Spike, so for what reason could they need any kind of servants?

Well, for whatever reason, Spike had decided to make things easier for himself and hire a maid to take care of a few things. The only thing is that Twilight doesn't really seem to know about it yet.