Grief
She stands there at the wall of solid white, the wall she knows the Doctor stands at, right at that very moment, in a different place. She presses the side of her head to the cold surface, places a hand there, and she can feel him doing the same. There's no way to explain how she knows it; she just does, she can feel it deep inside her heart, inside her soul. He's standing there where she is. And for that one tiny moment she feels like they're still together. Like she can still reach him.
But she can't.
She knows this, too, and she knows that someday she'll be able to live with that fact. But not for a long time. And right now it feels impossible, like nothing could ever fill the deep, aching chasm that his presence in her life once filled. The pain and emptiness feel like they will always be there, in small things, all around her - a flash of blue painted wood, the swirl of brown coat-tails, a flicker of a joyous smile. The Doctor will always be there. He will never be forgotten. And she doesn't want to forget, because that hollow, cold pain is worth having known him, having traveled with him...having loved him. It's all worth it, all bearable, because of him. The wonder of him. She'll never forget.
Hours pass in agony; she grieves for a life lost, and it's her own. Her life with the Doctor is over, and the thought is unbearable. After all they've been through, after all they've seen and heard and experienced...now it's all just gone. The hours turn into days, which turn into weeks and months and an eternity. The sadness and the pain get better over time, easier to cope with, but they don't go away, and she doesn't think they ever will. She tries to live a somewhat normal life with her family, keeping up a brave front for their sakes, but every single second she thinks of the Doctor. She can't stop. She's living not even a shadow of her former life, but she tries to make her new life echo the old in some way. She goes on adventures of a sort, but they're not what they were before. The thrill isn't there, or the excitement, or the gleeful abandon.
Or him.
Breathing hurts, moving hurts. Living hurts. She's learned to ignore the pain by now, at least to some extent, but even when she disregards the pain, the memories still flood her, and she can't ignore those, she just can't. If she does, then they'll fade further and further away just like he did and then it'll be like he was never real. So she holds on.
And now, tonight, she has a dream. A voice, calling to her, calling her name. And she knows she has to follow it. Because it's his voice, his wonderful, beautiful voice that fills her ears and her mind and makes her feel truly alive for the first time since she lost him. The Doctor is calling her, and she must go to him. She has to tell him, and this will be her very last chance. The last time she will ever see him again. She has to make it count, say all the things she should have said from the beginning, make sure he remembers. Because she'll remember. Forever.
"Rose..."