I'm getting confused with the difference between "politeness" and "conditional" especially when sentences contain "would."

Will you take a look at the writing below and explain why she is speaking the way she speaks in the underline part? In the story, she is a well off, bitchy person. I see no necessity for her to be polite or conditional.

I'd then pick up the phone and pretend to dial. There was no way I could get heavy-handed and demand that an English person send me money, even if he owed it to me personally. Holding the receiver up to my mouth, I'd look out across the garden and into the orderly homes of Valencia's neighbors. Uniformed maids entered rooms carrying tea services on silver trays. Men and women sat on chairs with four legs and
stared at their walls without the benefit of sunglasses. What worried me was the thought that I actually belonged in Valencia's house, that of all the homes in New York, my place was here with the Barefoot Contessa. "London's not answering," I'd say. "I think today is a British national holiday."

"Well, then, I think it would be good for you to call that store in Michigans who owe us the twelve dollars and fifty cents."

Thank you,

The conditional is used for politeness; in that case an 'if' clause is usually understood but not uttered. In the above case:

Well, then, I think it would be good for you [if you are willing to / if you want to /if it is convenient] to call that store...

By using the conditional II , the speaker demonstrates that the action depends on the listener's opinion/decison, not the speaker's opinion, and is thus more polite.
Thank you for the clear explanation. I should've asked you already. Emotion: crying