Sam, She has had many weeks to detach from you and the relationship. She is now treating you as a business partner and nothing more. Her empathy chip is broken, she has moved on to someone else and her feelings for you are now stuffed down so low that it may take a while before they rise to the surface again.
Do what you need to do to protect your assets/finances. Go home for the holidays and plan to move forward with the separation upon your return. I don't think she will be any friendlier upon your return so prepare yourself for a possible hello and nothing more. Right now, her focus is on her new friend.
Please continue to focus on you and what you need to do to get through the holidays...there's nothing you can do to change her course...let her go and so that she can grow up.
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.