Elizabeth, the Velvet Room attendant in Shin Megami Tensei: Persona 3, is a playable character in Persona 4: Arena. She has Thanatos as her persona and fires death rays in battle.
Margaret, Elizabeth’s sister and the Velvet Room attendant in Persona 4, doesn’t get her hands dirty. Famitsu says Margaret is in Persona 4: Arena, but only as a navigation character for the game’s menus.
Maybe Margaret was *too* powerful for Persona 4: Arena. That fight on the second play through is pretty tough… not Demi-Fiend difficult, but still pretty tough.