I agree w/Peace, they become very selfish, self-centered and spoiled brats. What they want, they want NOW. They do not understand that it takes time to process stuff and they become very paranoid and think that we are stalling in getting things done. In many cases, they have been the ones stalling and then psst! They think we should jump through hoops for them.
They do not care about us or the children. They only care about themselves and getting what they want. The holidays are a prime time for the good, the bad and the ugly to come out in some of them.
I would suggest that you try to maintain your cool and whatever you do, do not get into it w/her front of the kids or anyone else. I wouldn't be the least surprise to read that she's being very nice when she comes to visit...why? Because you are trying to placate her demands.
Dig deeper for patience, count to 10 before responding to her comments and do not be surprised if she tries to bait you. You have to be the best actor that you can be for now. Take a walk or a long drive and scream as much as you need to in order to let the anger out.
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.