Ursula is in love with Rupert Birkin. It is questionable whether he is in love with her. They are kind of dating, in the way Edwardian English people did that. Ursula (who is not 12 years old, but a grown woman) is sitting by the door waiting for Rupert to come visit her (unannounced, I might add). The day goes by, and he doesn't show up. So Lawrence gives us this straight from Ursula's mind.
Ursula, YOU ARE NOT 12!
She sat crushed and obliterated in a darkness that was the border of death. She realised how all her life she had been drawing nearer and nearer to this brink, where there was no beyond, from which one had to leap like Sappho into the unknown. The knowledge of the imminence of death was like a drug. Darkly, without thinking at all, she knew that she was near to death. She had travelled all her life along the line of fulfilment, and it was nearly concluded. She knew all she had to know, she had experienced all she had to experience, she was fulfilled in a kind of bitter ripeness, there remained only to fall from the tree into death. And one must fulfil one's development to the end, must carry the adventure to its conclusion. And the next step was over the border into death. So it was then! There was a certain peace in the knowledge.