I have a lot of empathy and sympathy for you, your friend, her children, and anyone supporting her/them. I would suggest that someone (someone brave enough perhaps, under the circumstances) be honest with her and tell her that her behaviour is pushing people away, and that it's hard to know how to support her when nothing seems to be good enough. At some point, if the behaviour continues, people are going to start backing off and she really will be alone. So you'd be doing it as much for her as for yourself. Also, if left unchecked, her drug and alcohol use could become addiction, if it hasn't already.

I am not suggesting that any of you are responsible for this (her behaviours, her coping mechanisms, etc), because none of you are. Even with grief and impossible circumstances, your friend is responsible for herself. It sucks, and it's true that maybe nobody can understand her unique situation, and she is certainly entitled to deal with it however she sees fit, but you and everyone else in her life are also entitled to have boundaries around it. All grief is complicated/complex. There is no set path/roadmap for people in any kind of grief/loss situation, and it's entirely possible your friend is doing the best she can. And maybe she won't listen to anyone right now, and maybe she will use any kind of intervention as a sign that people are not really on her side and push people further away. That's her prerogative. Regardless of the possible outcome, I wouldn't suggest just letting it go. It sounds like this has probably been going on for a while. Also there are children in the picture. And believe it or not, a lot of people who lash out aren't even aware they're doing it, whether because they're just not aware of their actions or because they feel like it's a normal response under the circumstances.

There were many things I never said to my sister because I didn't want her to feel judged; I wanted to let her know she was supported and loved no matter what. Her behaviours ended up killing her and I still wonder to this day if my intervening more urgently and earlier would have made any difference, but I never tried so I'll never know. I have no doubt that you all love and care for your friend, and that nobody wants to let go and leave her unsupported. But remaining silent as she self-destructs isn't doing her any favours. Also, right now, based on how you've described the situation, it sounds like she's being abusive (verbally/emotionally/etc). And no matter what state she's in, that's not something the rest of you should have to deal with.

I wish you the best in dealing with this, and hope any of this has been helpful.