Personality disorders don't just start out of the blue either, though. They're usually hereditary or related to childhood trauma, meaning that the symptoms are usually there from a young age. It affects your thinking and your behaviour and it never "turns off", so disordered patterns would occur very often on a regular basis in reactions to various triggers, not specifically during online lessons.
According to OP, this behaviour is very new and has never occured before, so I think it's more likely that it's a stress reaction or some kind of a mental break. However, it's pointless to diagnose her based on a Reddit post. Yes, she does seem unwell, but no one will know for sure what is behind it until she visits a professional, so all this speculation is doing is perpetuating the heavy stigma that people with personality disorders already have to deal with.