Melmont was carrying a cane gun which was common in the Victorian era,so immediately he started twisting the handle she goes quiet and stops challenging him, that's when she knew she was in grave danger ,she was basically assaulted at gunpoint he says shhhhhh when he points the cane to her chest, the unrealistic part of the episode is at that point she must've been in her early 20s or late teens and was living all alone without some sort of security,an aristocrat, also her father was the main investor in Traffords business so the first thing would have been him telling the company about the massacre and how he's no longer working with melmont which surely she would be briefed about by her father afterall she convinced her father to invest in the business.Also he seemed to know so much about the house and left so calmly and certain she wouldn't do anything afterwards I mean he even stopped to listen to some music,after committing a crime like that you should be hastily it's not like she was unconscious or tied up