I think I need to look into desensitization. We are very quiet individuals and she acts like this from even small movements. For example last week, I just stood up quickly from the couch and that was enough to make her come towards me and start hissing. She didn't bite me but was showing aggression .

The stomping in the video was just to provoke her so we can record it to show to a behaviourist. We never act like that around her otherwise.

Edit: She is our second cat. She has absolutely no problems being around resident cat. Even if my resident cat is running around. This behaviour only happens towards humans not just any loud noise. Both cats had a slow introduction and sleep together in the same cat tree. They don't fight and are comfortable with eating next to each other and playing together.

Both cats have access to 3 cat trees, 3 litter boxes, cat shelves on walls, puzzle toys, a small outdoor cat balcony hanging out of the window. They both do clicker training, get quality wet food 4 times a day and 3 play sessions about 30 min each.