@Nixnaw
Oh, thank you, I was debating on whether to read that series as either the manga or the webnovel.
@FireFox
Yes, the usage of the dress does make sense here because it allowed her to hide her sword.
I'm just suggesting the other outfit for when she gets to attend an actual formal event (that doesn't involve a surrendering King's murder attempt), so that she can have something nice, but not a straight up dress.