Well, Lucina is pretty much the best Falchion user (and second best Sword in the game, some would say), so she has that going for her. I liked Lucina before, but she wasn't really one my favourites; getting her in this game made her grow on me though. What's an AT, btw?
I've thought about giving my Camilla's Brave Axe to someone else too, but she's done so many things like carry Flier quests and cheese Narcian for me, I can't bear to do it lol.
@GuiltyLove but some day they'll let us promote her into Master Knight only if you have 5* Lachesis!