What you need most at this time is listening and companionship, listening to her talk about her pain, or telling you about the happy time with him. At this time, my mind is extremely empty, I don't know what I am doing, I don't know what I should do, I don't know what I want to do.
You don't need to comfort her, you just need to stay with her. When she has cried enough and let off steam, she will want to do something that seems meaningless, but she wants to do it. You just have to follow and protect it.