I think I completely bypassed the script - Astarion killed Auntie Ethel in two hits with Wyvern poison, and I'd already killed her little fey sheep. This early in the game wyvern poison is a real nuke, good thing I've only found two of them. Fortunately I didn't encounter any real "bugs" per se, but Ethel's body ended up teleporting down to the room with the cage. I did manage to speak with Mayrina, and she acted is though I'd killed Ethel right in front of her. I thought I wouldn't be able to complete the quest (because I told the brothers "good luck" to avoid making my party mad) but I ended up finishing this section when I found the wand and used it.