The anger is terrible because they are just plain angry at themselves and everything and everyone around them. The least little thing can set them off and that why living w/a MLCer is called walking on eggshells. The best thing you can do is leave them to their anger and walk away after you say something like 'I'm sorry you feel this way". Try not to argue w/them if you can. They are looking for validation as to why they feel the way they do.
I am sorry that she's acting like this w/the holidays fast approaching. Try to find things to do w/your family and leave her to her time and space. She needs to figure things out for herself.
People have opinions on what you should or should not do...but until they walk a mile in your shoes, they will not understand what you are going through.
Hang in there!
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.