Barty waited until she finished speaking before laughing lightly. Bells was willing to use almost any means, but given her reaction to this, Barty actually guessed she never would have agreed to it, had it been Vera's plan. But he didn't care to comment on other people because that was just guessing. Himself, he was sure of.
"I clearly do not need Vera to find you," Barty pointed out the obvious. If he wanted to arrest Andromeda, he would do so - confession to anything or not.