Nina was already someone who had an incredibly low self-esteem when it came to her appearance and how everyone viewed her, so it was only natural that she would have such thoughts when asked to degrade her self-value even further.
No matter how much she trusted in Kafka and how she had gained confidence in herself recently, she still couldn't stop the thought of Kafka disliking her after seeing her in such a dirty state, which was the main barrier from doing what Kafka told.
Of course, Kafka being the observant person, he was caught onto this when he saw the hesitant look in her eyes.
He knew that Nina wouldn't be able to decide if he didn't give her some reassurance, so he said to Nina in a gentle tone,
"It's okay, Nina...I know what you're thinking about right now, so let me just remind you that you don't have to worry about such insignificant matters."
