I'm not sure if it was actually tea she was having or something magical to simulate tea. It was at the Torchwood cafe in Everglade, where both the menu and the patrons are something else. And yes, she's a magical skeleton.

[ Look at him, making it sound like they're friends when "anon skelly" is his most-hated enemy in the five towns. But they did have a very civilized tea time. ]

I've learned it's sometimes best to... just not question it and accept things at face value. Saves you some headaches.