It's sad that the chapter is so short, but as other people have mentioned, she's also working on other projects. Japan has a serious problem with people working themselves too hard, so I'm glad she's trying to find a way to balance her workload rather than jeopardize her health. Also worth noting she puts a LOT of effort into her artwork that can't be filled in by just assistants, so I think this is also an attempt to make sure the quality doesn't degrade in favor of churning out more pages (just look at Hunter x Hunter, you can tell when Togashi is heading towards another hiatus because the art starts to taper off).
She COULD choose to just put Black Butler on full hiatus to focus on her other projects, but she doesn't. I personally like to think "something" is better than "nothing" in this case.