Why Sabirah Chose Delhi?

Sabirah's trip to Vyaspur to meet Zakir’s family:

What a long train it was, car after car. Which train was it?"
        "The Delhi train."
        She was amazed. "This train goes to Delhi!"
        "Yes, of course."
        She was silent for a little. "Zakir, you must have seen Delhi? What's it like, Delhi?"
        "I've only gone once, but after my exams, I'll go there to live."
        "Really! How?" She was astonished.
        "I'll go there and work."
        "Really?"
        Night was falling. The moon had not yet come out. But there were a few stars, twinkling like distant lamps in the expanse of the sky. I looked steadily at Sabirah's wondering face.
        "Sabirah!"
        "Huh?"
        "Sabirah, if I should get a job in Delhi then -- then -- " My tongue began to stumble. "Then -- we two can live together there." 

THIS is the passage I feel is the reason why Sabirah chose to stay in Delhi out of all the other places (Dhaka or Lahore). This fake promise made by Zakir is the reason poor Sabirah wasted her life in Delhi. She had hope that he would come after her hence she stayed strong throughout the novel but in the end when she realizes Zakir [FINALLY] has written letters to Surrendar which are concerned to know about her mother but not her, she breaks.

“I mentioned your letters to her. She said nothing, she burst into tears. I was astonished. During those days when the worst news kept coming from Dhaka, I always found her calm. But today she burst into tears.”

This sudden outburst points towards only one person and that is Zakir. He is the reason why she wears white sari and dresses like a widow. Even Surrendar recognizes the cause of Sabirah’s tears:

“My friend! May I say one thing? Don't take it amiss. You're a cruel person, or perhaps now that you're in Pakistan you've become so.”

But Zakir is just so slow and senseless. He still doesn’t comprehend anything written by Surrendar. He sits there asking himself “oh, Am I cruel?”

…Like Wow!!! Such a flat character.