She's finding it hard to cope - her hopes have been dashed, the future she dreamed about has gone and she's scared about that. There's nothing in its place. She wants you back. She doesn't want to let go of everything it meant to her.
Because the world seems horribly big and empty. Because the future is a very frightening concept when you'd previously planned on sharing it with someone. Because she's a girl, she's a romantic and she fears if she lets go of her dream, she'll live a nightmare. Because she has a hope and she fears if she lets her hope go, who will she be?
The effort, the pain of clinging on is preferable to the wide-open fear of letting go.
