I see so much strength and improvement with your R with your D. That's so great.
I guess they have a process to go through just like us...and it's not linear for them either. The holiday season by nature shoves all sorts of family stuff in our faces. I think it's normal that this would be a particularly tough time, because it's all about family and traditions which have now changed so drastically.
As for what to say to D... what can we say besides, "I'm so sorry you are going through this. I know it [censored], and I'm here to listen or help in any way I can..."