So I've started a new Dunmer Spellsword, and I got caught up in a war with some vampires on the way to Solitude from Dawnstar. So we sneak into the master vampire's lair, and I drop a couple of fireballs on him. He runs away up a passage. A few seconds later a message pops up that the master vampire is slain and to report back to the Jarl. Huh? So I sneak my way up the passage and spy a figure ahead of me. Figuring it must be hostile, I let go of another fireball and immediately get a message that I have a 40 gold bounty in Hjaalmarch. Crap. I walk up to the body, and it seems the friendly figure I killed was Alva, with Movarth's corpse lying a few feet away. Is this supposed to happen?

If you don't kill Alva in her house she'll appear in the lair, and will be non-hostile. She'll fight spiders and vampires alike. In a fight against Movarth she often loses, as he will likely be higher level.

Alva had left her house when I broke in to snoop around. I did kill her thrall, though. So is this is a bug, or by design? In my imagination, she had come to regret her actions and atone for them by killing Movarth. I just denied her the opportunity for a final speech before she killed herself.