I watched my nana die last month. Literally watched her die. It was a relief in the end.
My best to you and yours.
Relief or not, it still painful to watch someone you love pass away. I watched my father's health progressively worsen from mid August (02) until just before Christmas of the same year when he finally passed away, I was happy that he was finally out of pain, but ours was just beginning. It's been almost ten years now and I still miss him today.
OP, I honestly can't say anything that will make everything better, just know that in time the pain of loss will be easier to bear for all, but you still never forget. Remember the good times fondly, and cherish what time there is left.