Third circle diabolist lawyer, a junior associate of a defunct (by act of Rovagug spawn) law firm in Westcrown.
Probably somewhere in her 30s. (now canonically 37!)
Studied law at some abattoir of devil summoning wearing some centuries-old Inns Of Court type institution as a skinsuit. (Tentatively named [someone]'s Lodge but I don't know what Aspex the Even-Tongued's famous chancellor and head of the judiciary was named)
Solidly in the theoretically-elite-but-actually-poor-in-context social class. Sometimes eats food, on a good day.

(how short is she? it's been suggested from semi-canonical manga panels that kirisame marisa is 4'3"/130cm. i am not quite THAT extremist, and she's at least not mistakable for a child, but... pretty short.)