If there are no guards and girl is not a slave, what kind of girl fights back or what kind just takes the beating (Slaves are obviously not allowed to fight back).
I guess tsunadere slaves still could fight back, even if it means more problems for them and MC.
Anyway, fight back traits are Fighter and Assassin (they trained to fight, after all), Fearless, Aggressive, Tsundere and Malicious. Maybe also Adventurer and Tomboy, but not as much as the first ones.
Takes the beating traits are Broken Will, Shy, Meek, Nerd, Kind, Mind Fucked. Maybe also Impersonal, Fragile and Dependant, but not as much as the first ones.
What kind of guard/girl would be more interested in trying to solve the conflict by force before trying to talk the costumer down or even be a cause of a conflict
Noble (if customer is not as noble as she is, for example), Malicious, Tsundere, Aggressive. Shy and Mind Fucked too, as unable to talk down the costumer at all.
Cause of a conflict traits are Cleptomaniac because of disclosed stealing, Depression (bad mood = insulting a custumer), Clumsy (drop something right on the customer).
What kind of traits would help guards or girls to calm costumer down?
Charismatic, Sexy Air. Any "good" physical traits, as Bloodkiss mentioned before, like Abnormally Large Boobs, Long Legs and so on.
Maybe a little mind control with Magic Talent or Psychic traits. Artificial Body - not many people want to fight with a construct (maybe Manly too, but not as much as Artificial).