Forcing them to attend the sentencing, especially in cases like this, would not be in their interest at all, only in the interest of punishment and the victims families would this be a benefit.

See I think this is a bit dangerous to the victims families. This is a murderer, going away for their entire life. She has literally nothing to lose at this point. She could have hurled abuse at the victims. At the judge. Screamed incoherently. Self harmed. Attempted to harm others. There is no further punishment that we as a society could inflict upon her.