Here’s my 2c.
I’m not offering this as positive proof of guilt, but if you’re a student of body language and facial expressions, watch Ali when Maddy asks her if she killed her mom. While she’s saying she loved Barb, she’s shaking her head “no” the entire time. She does this once more shortly after in that same interview. It’s not a sign necessarily of guilt, but it reflects that she’s being deceptive or inauthentic. It’s rather obvious if you’re paying attention.