If she can get into a healthy environment, in time she will see things as they are. At her age she just wants to help her dad, more than that is a bit beyond their "real" comprehension. I went through several years of Evan really wanting to do an intervention for his dad.
She is at a critical age, hopefully her new environment is a healthy one and one that she can stay in, that will make all the difference, or at least give her a much better shot at it. If she can get to Alateen it would be very very good for her.
You can't listen to that and you can't enable it to continue. It is the best thing for everyone as you well know. It is hard to watch and hard to be in the middle of. I have been in your shoes and know what it feels like to be blamed for not fixing things, not taking care of someone else. Well guess what. You can't fix someone else, they have to do it. To make it easy for them...enables the situation to continue. This IS supporting him. Remind yourself of that, constantly. Everyone's rock bottom is different and some never seem to hit it. And someday, you may find that those who disparage you now, come to the realization at some point that their "support" is enabling the person to continue the behavior. They are in denial and you can't fix that either. They have to realize it on their own. And they may never do so. It is NOT your job to fix it. It has to be his. He has to want it bad enough. Only then does it have a prayer of working.
As to your mom's stuff, just go in and get that over with. On that one you really don't have a choice. The sooner it is dealt with the better and if folks take issue with it remind them they are more than welcome to do it. Or better yet toss it out there. Hey, I'm going to go clear it all out on xxx. Unless someone else wants to do it or go through things first it will all be donated to xxx in her memory. Or something like that.
Pre-emptive strike