Grace doesn't blame Kanako for anything, not really. Kanako is just a child, almost as powerless as she is, and she doesn't intend to make the fox's life more miserable than it already is. In the lab, when she has her bearings on what's actually happening, she presents herself as "Harmony", the helpful voice in the kit's head who talks her through her worst moments. She comforts Kanako, she counsels, she even sings to her sometimes (something she rarely ever does in front of others). One thing she never does is manipulate Kanako into into doing her bidding, because Kanako is a child, and she won't use children the way monsters are happy to use her. Nor will she reveal who she actually is, because Kanako is still traumatized by the "evil human" who hurt her friend (despite what it looks like, there's no actual ghost present).
Grace bears it, because Kanako is just a child, a child who lost almost everyone she cares about, and she needs someone to care about her. That stupid, cowardly lizard doesn't seem to; yes she looks guilty whenever she sees them, and brings toys when she visits; but she never seems to stick around for long, and certainty doesn't do the right thing and free them. As for the others? They are usually too lost in themselves to really interact with. It's very much a burden for Grace, but one she chooses to bare, rather than being forced too.