Sorry to hear of your troubles. Very common in this forum.
I can relate to you losing your daughter and her little family as I lost the affection from my youngest daughter of two last year. Actually I never had it in the first place as her mind was brainwashed by her mother. But I do have my eldest daughter and we are close.
If you put the following thread title in search above you'll read about some methods of avoiding more hurt than you are experiencing now
the best praise you'll ever get
anxiety, how I eliminated it
Now since those threads were written I've studied myself further to find that distraction and occupying myself are two of the most powerful self help ideas around. Filling your life with sports, hobbies and interaction (clubs) might not sound great as it means challenging yourself, but once established you'll have a few friends and you'll be able to at least convey your sadness and they can with theirs.
Essentially find enough activity to distract you away from your daughter and allow your other daughter to come to you when she feels she wants to. Then sit back and listen to her and her life...in effect, be a mum. If the topic of your estranged daughter comes up simply say "oh well, she might come back one day, I hope so, it would be nice to have a united family again" or similar. I wouldnt involve her too much, in fat she is likely hearing the other side of the story from her sister and could be influenced.
There is no straight remedy to these situations but in the years you have left, you can live it with sadness most times or you can enjoy 90% of it and the other 10% think about your family's demise and loss, make that grief as short as possible then back to enjoying life again. I think about my other daughter on occasions and wonder how it could have been without the emotional abuse that she learned from her mother.
Use search- losing a child
I hope that helps.