She would have to consent.
She can consent with her attorney's knowledge and approval.
Or she can consent going against her attorney's wishes.
Either way any competent police department is going to get on video an unharmed, unbattered, rational prisoner stating that they know they don't have to go and are complying of their own free will.
My guess, and no one is going to like this, but we have seen the black eyed photo of stepmom, we have seen the dramatic change in her appearance, and we have seen biodad arrested, I said from the beginning this would spin down to a he said she said, who flips first and who provides real evidence first. I see a battered wife defense with the stepmom coming down from a mile away.