I bet that's where the problem lies. I agree that smoke shouldn't have killed them that quickly, especially if the enclosures have a somewhat restricted airflow. Plus I'm thinking they would have ended up with an URI rather than dying. Unless sage has a toxic chemical, but it sounds like it doesn't. Maybe it wasn't sage.....
Since your aunt didn't like the smell, I could definitely see some Lysol/smelly sprays/perfume being used and your aunt didn't even think about it's effects.
I would think that if the heat element got hot enough to kill the snakes that there would be some sort of evidence of that. Burns/melting/etc.
So sorry for your loss. That really really sucks![]()