I just told Karlach I might have something to cool her down, thinking it would be an in-dialogue prompt to use something I didn't realise I picked up. But no, that sent me out of conversation.
Now she says "I'm waiting" when I speak to her.

I threw an Elixir of Fire Resistance at her, with no change in her dialogue.
I threw the Icy Crystal at her, no effect.
Is she expecting me to hit her with an Arrow of Ice?