Theory:

     Satish's mother said: 'It’s such a nuisance having to wait for the train right in the middle of the night. But one can’t let the child wait here alone. Anything can happen to a boy at a big station like this, there are so many suspicious characters hanging about. These days one has to be very careful of strangers.'
 
     'Arun can travel alone though,' said the woman beside me, and somehow I felt grateful to her for saying that. I had already forgiven her for lying: and besides, I had taken an instinctive dislike to Satish's mother.
Explanation:
 
After knowing the train would arrive late at midnight, Satish's mother said it was completely inconvenient to wait for the train late in the night. She also said the railway platform was not a safer place to leave the children alone. Anything could happen if a boy was standing alone on a platform. There might be many strangers roaming here and there in the station. The strangers would attack someone, and she said as one has to be very careful with strangers and maintain distance from them.

After hearing the lengthy talk of Satish's mother, the woman beside Arun said, 'Arun can travel alone though'. Arun felt thankful after hearing her words. When the woman introduced herself as Arun's mother to Satish mother, Arun felt discomfort in that. But after hearing the woman's faith in Arun, he had forgiven her for lying. Arun started to dislike Satish's mother as she was very talkative and treating the woman near him as a poor lady. And also, Arun hated the way Satish's mother was speaking to him.
 
Meanings of the difficult words:
 
S.No
Words
Meanings
1
Nuisance A person or thing causing inconvenience or annoyance
2
Suspicious Having or showing a cautious distrust of someone or something
3
Grateful Showing or expressing thanks
4
Instinctive Relating to or prompted by instinct; done without conscious thought
Reference:
State Council of Educational Research and Training (2019). Term-3 English Standard-8. The Woman on Platform 8 - Ruskin Bond (pp. 107-114). Published by the Tamil Nadu Textbook and Educational Services Corporation.