I read a little of this manga several years ago, so I don't remember much of it. I'm PRETTY sure she had red hair, she might have been in some form of military, but all of her fellow soldiers were killed. Also, there was a painting of a tiger or a wolf on the wall of the fortress, or something like that? It's really only coming back to me in pieces, but I'm pretty sure there was also some kind of part where she was a man at one point and that guy maaaybe died? Like, I wanna say he was executed? Is this ringing a bell for anyone?

Edit:
Also, I'm pretty sure the title of the manga is a nickname people give her, because she ends up being infamous or something. It has some sort of "kill" or "murder" type word in it, I think.

Shut Hell maybe?

Yes, that's the one!! Thank you so much! It's been bugging me for weeks!