Thanks to Serana's programming of being able to interact with the environment like other npcs would on her own, I ran into this funny incident. Where she is currently, there was a dying (now dead and his corpse thrown to the other side of the room) mage/researcher as part of the mage's college questline just within Mzulft. Serana decided to help herself and interact with the only thing she could in the room, leading to this. Fortunately, you wont have to worry about her dying on you like the guy from previous.
Maybe she's irritated that her programming forces her to do these kinds of things, including sweeping. As to the armor, its the Lustmord Vampire Armor. It doesnt have to be for vampires specifically though, it was just designed with them in mind. Also, sorry for the 5 day slow reply.