The yandere stuff doesn’t have that much content aside the yandere events and the “Damaged” quirk that doesn’t do much yet.
But if you’re worried. Gwen won’t harm you or any girl in the harem.
She wants to see you happy at all costs, even her own life. Harming other girls in the harem won’t make you happy, so she won’t do that.
If you’ve played the main story and saw the cupid, you may get an idea of what you’re dealing with.
But for now, the yandere stuff is mostly just a slight annoyance.
Maybe in the future it will get more content, but you won’t have to worry about you or your girls getting harmed. Not that type of game.