To quickly summerize the parts with Mori that make sense and the parts that don't
>SKK meets Mori very early in her life.
>This is during the part of her life when she is putting on her fake smile while others are bullying her.
>Siren's event happens "way later", after she attacked that Lumi Rikker and started being hostile and on edge around everyone so they wouldn't bully her.
In the bond story, Mori acts differently and is far easier to interact with. This makes sense since this is the part of her life where she fake smiles and hides her feelings. In Siren's event, she is different. Her fake smile is gone, and she is cautious around everyone. Her bond story explicitly says a lot of time has passed when the story cuts to SKK walking through chapter 37/38. In that timeframe, is where she attacked that Lumi Rikker and was sent to the Rehabilitation Center. This is where she turns cautious and on edge around everyone, and meets the malice of others with her own malice.
>the parts that don't make sense
Saying that nobody has ever shown her kindness, nobody has extended a hand to her, nobody cares for her, and or wanted her to live. This is not true. SKK did that. He searched her out, extended his hand to her, was kind to her, called his squad to train her to survive better and not walk into the same issues, and reached her all of that because he wanted her to live. This is just ignored
Nobody here minds character interactions, but people "DO mind them" when they are actively disenfranchising and devaluing the interactions the Nikke have with you in sacrifice of that, which leads us to Siren's situation where she's having schizophrenic talks with herself and her bond is not even a bond story.