That’s not uncharacteristic? Zoro not wanting to and not liking people hurting women has been a thing since EB. Tashigi called him out on it in Loguetown and he called out Enel for it
Yes, but he has never had any problem with it if forced to. Tashigi specifically is the ONLY other time he outright refused, and the reason given was she looked so much like Kuina that he couldn't bring himself to. Not that she was a woman. He has beaten down enemies who were women before, if they were an actual threat/trying to harm him or the crew he never even really questioned it.
Part of Zoro's character motivations is about having excuses based on something like biology (like Kuina talking down on herself because she was born a girl), he even references this in the King fight when King claims Zoro is biologically incapable of defeating him. He outright says he hates that sort of reasoning.
So yeah, its weird af that he sees someone who is clearly powerful in the process of trying to murder his friends and holds back when he could oneshot her.