It's hard at first. How does she mourn those who have been lost? It's not an easy task to remember someone who has barely left, who was just there. It takes time for her to create a routine in which she can grieve, but oh does she grieve. It seems as though she is made of tears and whimpers. Some days that's all that anyone is made of.
She misses the lingering lost ones, many of whom she never had a chance to say goodbye to. The memories are still there, but it's no secret that the details, once so vivid, will fade into darkness. The smells and colors and laughter will crumble like ash.
She knows that there is no bringing back the dead, not in any way that would be productive, at least. And yet, she would if she could. She would bring them out of eternal slumber, back to the waking life. She would trade every bit of calm and peace for a glimpse of the way things were. She would do it in a heartbeat, and she hates herself for it.
Harry has to pull her out of the dark when she can't bring herself to do so. He kisses her lips and brushes back her hair. He wipes away any tears and promises her that it will get easier and that life will progress normally, they just have to try harder, you see. If they just push and push, they'll break through to the other side and everything will be better. They just have to keep trying.
Harry tells her all of these things and she tries to agree with him, but they both know deep down that he doesn't believe in his own words. He is, after all, nowhere near the same Harry, and she hasn't been the same Hermione in years. They were robbed of themselves, and trying to be the same people in that situation is like trying to complete a puzzle with half of the pieces missing. You can't even make out the picture.
She thinks about everyone that has gone and what they all meant to her. She has found that in one way or another, they all affected her. But those thoughts always bring her back to Harry. They belong to each other forever, but he is not the same person. He can never again be the boy on the train.
Despite everything else, that is what she misses the most.