It's not that sad. She used to brag about trying to seduce her brother. Talking about crawling into his bed to rub against him, shaking her ass at him, constantly degrading and insulting him to lower his self confidence and make him think no other women would ever love him. She fucked her brother up hard, and he was lucky enough to have friends to save him from her manipulation.

Kirino is just a fucked up human being. You should not have sympathy for her after all she did to destroy her own family. You should feel bad for her brother that she tried to isolate and make into her sex toy. It was only thanks to the friends he made that he managed to escape her.