She's not really surprised. Goro Akechi is never above making threats. That said she still thinks he's far too forgiving of someone that clearly is too busy wallowing in self pity to make amends for what he did.

"Boo- fucking- hoo," she mutters about Maruki asking Ren to make an unfair choice. "If I wanted to hurt him I could have done it already." Which is not untrue. She could have tried to strangle him in the middle of the Tokyo street, if she really wanted. "Can you go play mother hen somewhere else instead of ragging on me for nothing?"