Grrrrruuuaagh! Oh man. This story had me squirming. I loved it! As Unblinking noted, the best part was probably how Clara - and society in general - had adapted their ideas of decorum and propriety to the reality that some people occasionally hatch monsters and other people have mouths inside that they use to eat them.
Clara was a particularly horrible creature, and I found myself really wondering where she came from. She was an interesting mixture of detached and quite inhuman, constraining her hunger only because it would be inconvenient if she was thought of as a monster, but also at least a little human. Her somewhat attenuated compassion for her client was interested. She appreciated his thoughtfulness, understood that she was providing a valuable service, but clearly did not feel any sense of human warmth towards him.
In that sense, Clara actually reminded me of an accurate depiction of a sociopath. She wasn't a particularly murderous being, she just didn't see her "fellow" humans as entirely real. They only mattered to her in that they provided something of worth to her, but if they did, she could be quiet warm and charming
Overall, I loved this one. A great, dark, bloody little horror story, with just enough explication to draw me in while leaving me wanting more.