Wow, all I can say to that also is that like your sister, where there is an end of the rope, the end of the script for the actor, & the balloon gets so full it bursts.
My gut feeling is that you just haven't arrived at that point yet........but I would strongly suggest that if you continue on this path, the end of the road won't be a good one for you & that NOW is the time to get some real help with what you are going through.
Sometimes we have to put a halt to all the wrong things that are going on around us for everyone's well being.....it's not easy....it's a lot of work & a lot of hopefully team work from all your sisters & as much family as you can get to join together.
I am sure you have a strong sense that the direction this is going to is leading to some really bad things that one can't really predict accurately without professional help......but right about now I would start regrouping & putting together a plan of action so that the disaster that is looming in the future can be avoided.
With any change, there is pain, but sometimes the pain we go through now with the necessary change is a lot less than the pain we end up with if the changes aren't made.
Hopefully you can get the right professional help to guide you all together in the right direction to not only help yourselves, but truly help your mother who sadly needs some "tough love" from all of you.
Many

for you & all your sisters & family......& much strength to get through all that is ahead of you & my best wishes. I know that I could not have lasted as long as you have without completely blowing up at everyone.