What’s the logic behind someone who can talk about you behind your back to people but get terrified once you’re back in the room?

I had an argument with a colleague who’s currently training to be a manager (She asked me why I was in the staff room but only had the guts to ask because her tall male friend was with her). After the argument, she then goes upstairs and talks about me to other colleagues and reports me to a manager. Once I returned back upstairs she was unable to walk in that same room by herself and looked absolutely terrified. Her friend also told me that she got angry at him for not following her up the stairs. Why would she treat him like a boyfriend? What is the logic behind someone who does this?
What’s the logic behind someone who can talk about you behind your back to people but get terrified once you’re back in the room?
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