I feel sorry for her, but love can't save psychosis like that. She did this all to herself. She had Yuki, she just let the yandere side of her get the best of her. Normal yanderes can keep that shit under control, especially when the object of their affection is actually starting to love them.
I wasn't expecting it to happen, but she actually tore that entire house down. It's sad because Yuki is going to have to kill her, and if he doesn't I say he's gonna get killed somehow and Yuno probably kills herself afterwards.