Angelista is a character referenced many times in game. With such items as:
The majority of the items suggest that Angelista is a priest. Three out of the five armor pieces bearing her name are cloth, two of those three are preferred by healing priests, and the other is an offensive spellcasting piece fit for a shadow priest. Angelista's Revenge and Angelista's Touch seem to break this presumed pattern, The former being a melee DPS ring and the latter being a tanking ring.
Another reference worthy of note is located in Stratholme. In Festival Lane, there's a shop named "Angelista's Boutique". The location of her store suggests she could have been risen as a member of the scourge during the Culling of Stratholme. Angelista does not appear in the Caverns of Time.
Angelista is listed in the "Special Thanks" section of the WoW credits, and is most likely a friend or relative of a Blizzard staff member.