Just visited the abandoned fort just to the south west of Whiterun, the one infested with bandits. I dismounted and got a closer look, which resulted in my rather over protective horse running right into the middle of the fort and kicking everyone in the face until they stopped twitching. Since she had already cleared the way I thought I would see what I could find inside. Long story cut short, I stabbed everyone to death. Unfortunately in my blood lust I burst into a room with two bandits and an elf named Agnis. I waded in and slaughtered the two bandits, Agnis suddenly appeared with a dagger and so quickly I impaled her on my sword. It was then it occurred to me she might have not been a bandit and was a prisoner! Did I just kill an innocent hostage or was she just a named bandit?

Yes, I saw her too.

She doesn't do anything (Generic Dialogue about how she lived in that fort for many years)
But seeing how the Fort has three doorways I can see her being used in a later quest.

Ah. I did briefly see a talk prompt appear as my dagger and sword plunged into her. Whoops!