I have a bit of advice I am going to reiterate for friends and family of grieving people. Probably this applies to people around me, but I know a lot of people who are grieving on these holidays. As I have said before on this blog, my father died in May and I am just now coming out of numbness and into feelings about it.

My best piece of advice: please don't expect your grieving loved one, or loved ones, to be able to conduct Christmas in the usual manner, or tell them/imply by action that they should shake off their grief for the season, don't wallow in it, or whatever insensitive things people come up with.
People who are grieving may not be able to indicate that they don't want to hear such things. Put yourself in their shoes and think about how you want to be treated.

Also, for people who grieve at this time, I have a link to a list that really helped me:

https://whatsyourgrief.com/64-tips-grief-at-the-holidays/