"I met the one who was here previously. She was markedly more ... stable than the one who is here, now."

Just throwing that out, but there is certainly some element of warning in there, for all the conversational, casual, tone.

"It wasn't her. It was her dominant." Who is stable but that just means consistently terrible. Really, really, terrible.

He still doesn't know what Joker was playing at, in stepping in and 'rescuing' Bruce.