It seems I missed some details the first time I read it, so I'm glad seeing this again to notice these things.
While I like the story thus far, there are some things that bug me a bit... No matter how skilled a swordman may be, they can't go beyond the power of the tools they use. It's general knowledge that mithril is supposed to be the toughest metal out there, so unless her sword is made out of mithril or a stronger metal, or she has imbued it with magic, there is no way that the sword could have cut through his mithril chainmail. No matter how sharp it is, or how hard she hits, it's impossible.
Just like the issue with her dueling in a dress, that is not how a capable swordman would behave. The author seems to be adding these little details "to show how good she is wielding a sword", but honestly it feels like it would only be believable if you had no idea how sword fighting works.