I think you are misinterpreting what this poster has said.
It's not blaming the DD to contextualise the long term behaviours of all members of the family in understanding this serious incident.
Rather as that poster has said, understanding this should rightly look to consider the long term actions of the father in validating, encouraging and rewarding his DD behaviour against her mother to maintain his favourite status.
The priority here is the welfare of all the children.
Achieving that demands the investigation into not just the incident but the family dynamics in which that incident occurred.
Addressing concerns contained only to the incident itself is dangerous and not in the childrens best interests.
The OP is out of the home getting MH care.
Does that mean these 3 children are safe?
They are with a father whose only reaction to his wife being admitted after assaulting their DD was having to actually step up and do even minor level parenting he has so determinedly avoided for years in taking them to hobbies.
Think about that. He's so concerned about the children he'd rather have her at home after what she has done instead of getting help because he's going to have to be a Dad rather than Mr Fun.
The DD's behaviour needs to be considered not as a matter of blame, but to explain the root cause of this incident which is years of abuse towards the OP by the father which not unexpectedly has resulted in the two older children replicating similar behaviours.