I have read your sitch and sympathise deeply with how s**t you feel right now. You have a choice to make here - either accept that she chose to inform you that she's going to the movies and be thankful that she at least had the common courtesy to let you know rather than just doing it, and to use the positive (that she told you) to give you the strength to leave her alone & let her do what she needs to do. The alternative is to spend tonight and probably the next several days steaming away to yourself, getting worked up, frustrated, cross, angry etc etc etc. Yes she is behaving badly, but she is confused and not being herself right now she is not doing this to deliberately hurt you - its just what she feels she has to do. She is behaving like a teenager so the more you can try to manage your R with her to reflect that fact, the more chance you have of moving forward to a constructive R in the future. THink of how you behaved as a teenager - if your Mother or Father reacted badly to you meeting an undesirable friend what would you have done - probably found a way to carry on seeing the friend without them knowing and probably carried on the friendship a lot longer than you might have otherwise done if they'd stood back and allowed you to find out for yourself that your new friend was not all that you thought they were.
Food for thought?! I have been through a similar sitch with my H and after many months (but not as long as some here) I am beginning to see the start of rebuilding my R with H, R with OW is over etc. You may not want to hear this, but even with so many positives in having got to this stage in my sitch there is still a rollercoaster which causes immense pain at times and I still have to apply the DB principles to avoid screwing everything up - and yes it is still a challenge to do that when there are times when you want to scream and shout and tell them how hurt you are etc.
You can do it if you believe you want to get to the point of being able to tell yourself you did everything you could to make the R work, and either it will or you will feel a better person for having tried - if only for the kids and your own self esteem, don't let the heat of the moment drive you to do something although you do not have control over your W you do have control over you and how you behave.
