@Beatrice It kinda is just for the fact she wants to pursue a relationship with him and be involved in his life, not to mention that she's tried to have sex with him. You probably would want to know if your best friend and crush was not only suicidal, but was being sexually harassed by an older partner who coerced them into sex during moments of distress and actively kept trying to get them alone and isolated from both you and everyone around them, ultimately hoping to run away with them and start a family.
Kinda important information given how close they're meant to be
Damn, does it make me happy that Chako realized she was being a dick. I hope she doesn't become someone who "saves" Rei, but rather walks with him and supports him in improving his life.
@Tamerlane That's entirely a one-sided affair on Chako's part. Reiji had no idea of her feelings then, and she was more concerned with graduating at the time than him. Even now, he's got no intention of pursuing a relationship with her (or anyone). Just because you're friends, doesn't mean you can't keep your privacy. He already told Chako about Nagi, who was a way bigger deal with the suicide clause. Yuri was irrelevant by comparison, because Reiji doesn't really know Yuri's intentions either or the real threat she poses. Look at how carefree he was to tell Chako he slept with a second woman. It was no real secret to him, and only did so when even loosely prompted.