Yes and no - psychotic episodes aren't in themselves dangerous, nor do they cause permanent damage on their own; that being said, they are *never* harmless and they can *sometimes* lead the person to do dangerous things, but usually just to themselves. Psychotic episodes are literally just somebody "breaking" from reality, and this can happen to do countless things and manifest in countless ways.
When dangerous people get psychotic episodes, that's where the largest problems come into play; it sounds like you had the unfortunate experience of encountering something to this effect. I hope you were alright, that's gotta be rough to encounter that.
Edit: Narci is in a dangerous position with it because of how psychologically fragile she is and how she paints a massive target on herself, making a potential vulnerable person incredibly moreso than before. She's much more likely the type to self-harm from what it seems.