Why does this vampire with a knife bother you so much? What would be better? S. Stone with an ice axe? But that would be much closer to reality + it wouldn't offend the memory of fans of Might and Magic 1-5!... And considering her freckled chest, it's quite possible to consider her undead....
IMHO, a sword for a vampire is a matter of taste... for example, if a player fights every day... and not just once... wouldn't the vampire get tired of drinking blood from anyone? His fangs might even wear out....
Let him wave a sword in battle, and have dinner when the opponents take their turn......