I don't get the impression you are trying to blame anyone. Rather it seems to me that someone oversimplified this tragic situation - perhaps due to a lack of information about your friend and filtering everything through AA vision - and that has been confusing and hurtful. I can totally understand how you might feel that way.
If it were me, I would ask myself whether I could just let this go, or whether it was something I wanted to bring up either with this person alone or with the group. In your view, as someone who knew this person, it was more than a 'step 6' issue, but also about this person being let down by mental health services. If we are speaking about not blaming, perhaps it is relevant to ask whether your friend 'S' should shoulder it all when public mental health services might need to be held accountable. It's about truth and honour. I don't see why anyone in AA should be threatened by that.
I'm really sorry for how you must be feeling (((hugs)))