We know she has chosen to stay through past domestic violence incidents. There are always various reasons. Could be financial. Could be that she thought she could protect her children better if she were there. Could be emotional. Could be she thought she’d be killed if she left. Could be a combination of the above. But given that past decision, she could reasonably fear being seen as complicit in the abuse that resulted in her child’s death. Not to mention that she’s already lied.
I can’t emphasize enough how terrifying of a position women in abusive relationships with kids are in. The possibility of their children getting unsupervised visits with the abuser is very real (if not probable, especially if the abuse to date has only been directed to the mother — but as we can see in this case, even after a conviction for child cruelty, it appears he still had custody of those children). And there is the very real risk of getting killed yourself if you leave.
All MOO. Not offered as defense of any action or inaction, just as possible explanation.