Although my DIL's father was quite ill and he'd been given 6-12 months to live (the 6 months would have been in and around Christmas), his death has really affected her deeply. His birthday would have been on Christmas day so that only increases the sadness. I know everyone grieves in their own way and there is no "right or wrong" way. We all want her to be apart of the Christmas celebration. The other family members (her family) seem to be adjusting quicker. My heart goes out to her. I lost both of my parents in the same year so I do know how difficult the holidays can be. Any suggestions as to try to help her through this......
Christmas was always special for our family because of "C-A-B": Christmas on Dec 25th, Mom and Dad's Wedding Anniversary on Dec. 27th and Mom's Birthday on Dec. 28th. My Dad died December 26, 2007, and after his death, Mom and I lived together until she entered the local nursing home in May 2017. Mom died unexpectedly at age 87 in September of this year.
I know that I feel Mom's death deeper and am more open about my grieving then my Brother and his family because Mom and I lived together for 9+ years and because I have no husband or children--Mom was MY WORLD. My Brother and his family live in different states and both of his children recently got married and both are expecting babies so his focus is more on them then on the death of our Mom.
I was supposed to have Lunch with my Niece and her husband on Saturday (they were on their way to his parents' house and stopped by for a couple of hours on the way), but I started to cry so hard when they arrived that I couldn't go.
Invite your DIL to your Christmas celebrations, and be supportive and understanding if she declines to attend or leaves the celebrations early.
Mum's partner of 27 years died on November 26. She is not feeling much like Christmas this year. We are changing things up.
It maybe too late now, buy my community has a Blue Christmas service each year. The local churches rotate which one will host it. It can be quite healing, even for those who are not strong in their Faith. It lets them see that they are not alone in grieving at this time of year.