As always, she keeps herself hidden.
It is not through lack of effort on his part. He returns, far more often than he used to. Her sister becomes almost annoyed, until she sees her expression each time. She does not normally show her feelings on her face, but this time, she does. It's fear.
It's impossible to say what the girl is afraid of. She is afraid he will keep trying, that he will find her, that he will discover her secret.
She is afraid that he won't.
She is afraid that he will hate her, that he will look at her with disgust, and she doesn't think she could bear that. All she wants is to be surrounded by love; she dreams of a large family, of reading stories to enraptured children, watching them grow up and learn about the world.
Of course, her condition makes this impossible. But she can dream. A dream does not cost anything.
So, he keeps coming, and she keeps dreaming, Until one day, she is forced into a rude realisation of what exactly it is that terrifies her.