A different kind of poison? Only lethal in high doses. Not lethal in spider bits clearly even if Peter had felt like he was going to die. There's a big difference between feeling like you were dying and actually dying.

It's not a poison she has heard of though, perhaps it doesn't exist in her world.

"Would she have been being mad?" She's a little more confused at this part of the story. His uncle, the thief, had been killed and Peter had been bitten around the same time. She can understand keeping nearly dying a secret though, it's a weakness.