Hold on. So Shiika witnessed Yuri's death, didn't try to stop it, and let it happen so that her father would be punished and she could be taken from her father to be put in a better family? Christ that's so messed up. What next? The father is also a victim?
Not quite. She witnessed Yuri getting R**ed by her father, who, apparently was also abusive towards Shiika, which was already hinted at but confirmed with that picture from the phone. If I had to guess, she didn't call for help when Yuri was in trouble because she feared her dad more than she cared for her friend, and/or felt momentary relief that her father's abuse was directed at someone else. While not confirmed, given the PoS's personality, there is a distinct chance she was also molested/r**ed by her father.
In any event, blaming a what, early elementary school kid for her death, because she couldn't call for help in time is still out of whack, even in a "worst case scenario" (that being that Shiika was somehow complicit). Even us adults can freeze under pressure, or when confronted with things we find disgusting or horrible, so automatically expecting better from someone who's birthdays number in the single digits is kinda insane to me.