If they're just super crazy obsessively in love without any sense of danger for any of the people invloved, I believe that's actually called Deredere.That's a very common Yandere type, but it's not quite as specific as to be just that. Yandere is basically just a girl with an unhealthy obsession, she doesn't have to be jealous. A girl who is chasing a guy who has a girlfriend and keeps on trying to join them and make it a threesome for example, that would be Yandere even though she isn't jealous of the girlfriend or trying to get rid of her.