>>19191851Rushia was a frequent visitor of the Holohouse, and expressed a lot of gratitude to KanaCoco's hospitality. They were good friends, and Kanata's shock is proof of that.
Coco talked about venting to Holomem, and one of those people is undoubtedly Rushia. Being retarded, Rushia probably took the hysterical rants of her fellow woman as truth, and was outraged at Cover for their treatment of Coco.
In a last ditch attempt to save her good friend, she contacts Narukami to expose Cover, much like she tried to do with her own issues this time.
That explains why she is so trusting of Narukami and Korekore, she was "helped" by them in the past, and she thought they would have her back again.