Miyu was unfair to Ilya.
After all, as clever as she is portrayed, she was not able to see her friend/comrade had been hit with a poison blade. Even Rin was not able to think quickly enough.
Miyu could always say that it was Ilya's fault for not being able to guard herself from the blade, but Miyu did fail before and Ilya helped her.
In the end, everyone else left Ilya alone in a deadlock where she was about to lose her life. Or at least she clearly believed that would happen. Then a self preservation mechanism created that explosion to wipe everything around so that she survives. Of course that might have killed the others. But they had abandonned her to die by then, so they can't be all that mean again after the fact. Unless they really don't care about her.