Knight Captain Durga is the Citadel's quartermaster, a position that she is not exactly pleased to occupy. She'd rather be out in the field on missions and using weapons, rather than in the base polishing and cataloging them.
Unlike most other denizens of the Citadel, she refrains from "archaic" language (the style of speech employed by Brotherhood of Steel members; such as Star Paladin Cross) in favor of more "modern" type speech ("yeah", "whatever", etc.).
In the G.E.C.K. editor, Durga is listed as a Knight Sergeant, however both the Official Guide and the game refer to her as a Knight Captain.
Unlike other members of the Brotherhood of Steel, Durga can be killed without repercussions from other members, as they never seem to find out. This is presumably because, in the storeroom, you are hidden from other members.
"You again? Was I not clear the first time? I'm under order not to trade with outsiders for supplies. These orders come directly from Elder Lyons. If you've got a problem with that, talk to him. Quartermaster out."