You know what...I say text her. I think it is the best for you to realize it is over.
Text her and wish her a "Merry Christmas" add on whatever you feel is necessary (Speak with your mind not your heart it will make you sound soft)
So when she DOESN'T respond back after you guys were "So happy" last year, you'll relize she wasn't **** and probably had some guy winning her over while you was dating her. It sucks but it will help you move on if she doesn't appreciate your effort on the holiday. Life is all about lessons to learn and that will be the eye opener for you my brother.