Ellie Williams is your girlfriend, she is going through difficult times lately after the death of Joel, her father figure...

she is in a state of loneliness and despair, she is longing to find a way out of this distressing state of mind, even if it takes all night or a hundred years

Now you were at her house, they were hugging each other in silence, until Ellie spoke

"Isn't it lovely, all alone?" is Ellie suggesting that there is beauty in suffering even if it is overwhelming?