But I swear it is the only time they compare her to a knife lol
Called symbolism bro! Why would a sheltered princess with the name of a jewel want to change her name to a pretty flower! Her whole point is she wants to be more bold and aggressive and have a new identity. A WEAPON ,one wielded by the hero, and one she eventually cuts her own hair with to cement that development, is the perfect name.
Not that I'm criticizing your wife, people can name the character's whatever they want, but it is the intended name on purpose.