My workaround - I ended up fleeing, re-engaging in combat with Dallis (Alexander doesn't rejoin if you do this), defeating her again (still doesn't die), then running away to get far enough way for combat to naturally disengage (then waited for her to stop searching for me, go to the Fort entrance, and disappear).
I did find a potential bug with flee doing this:
- If you flee, but your enemy is close enough to the portal/statue, you'll instantly be re-engaged in combat, just at the statue/portal location (you can keep trying to flee, you'll never actually escape). I'm guessing flee uses the closest statue/portal, which in this case was right next to the fight.
