You guys are way too up in arms about sis Riko. Sis Riko is likely not a bad person, so it's unlikely she hurt pink Riko out of malice. It's more probable it's a fairly standard trope of she broke up with pink Riko to "be normal" and fit in, possibly while denying her own sexuality along the way, as unnatural. She might also be a victim of the system, although of a different kind, so there is no reason to be so hostile before we know what actually happened.