Just tell her you are very sorry that her dad had passed away, tell her to take as long as she needs to grieve and eventually she will have to let it go, because life goes on.
Tell her to remember the goods years they had together. She is fortunate to have him for so long. My dad died when I was 6. I can't remember much about him.
If she feels low, tell her u will go out with her or chat on the phone. Help her with funeral arrangements.