Yup, as others have said @kurtsimonw time is a healer. You will feel shit today. The same tomorrow. The same next week, but then one day you'll make up and feel a little less shit. You'll get there!
Try and limit contact with her but I know that can be difficult when you work with someone, but try your best.
Have you got any holiday to take? Get yourself away with your mates. Socialise. Enjoy Christmas the best you can. You will get through this.