Because Isabella wants to know about MC and girls, not about his father, mother or something else. Her interest is in knowing how he would treat Jill, how he is with women, or at least that's how I saw it in the conversation they had at lunch.
In other hand, Zoey doesn´t need conection with others character to create more drama, just the fact that Zoey exists is all the drama the MC needs.
That could already be the case.
But DPC writes his stories in such a way that he often reveals in advance what will happen later. We just can't always interpret it correctly because we can't see into the future. (Please do not start with time travel)
Example:
When Derek sent the MC a photo of Cathy butt, Cathy thinks about it.
"(l...l'm not sure if I should feel offended or flattered.)"
"(Probably a bit bf both.)"
"(Although it's funny how men see me as attractive in real life...)"
this foreshadows the later part with Cathy's chunk and the conversation with MC.
These "coincidences" can be found throughout the game. To make it clearer, here is another example:
Maya and MC in the meadow!
MC: "It's times like these I wish I was rich."
Maya: "You're jealous of what they're doing?
Maya: "I can buy you a lemon, if you want one."
MC: "Haha, no! I just meant in general."
Maya: "What would you do if you were?"
MC: "I'd help you out with the tuition."
No one knew about MC's heritage then. But it's a hidden preview. And I don't think it even refers to the $5,000. I would imagine that the MC's inheritance is much bigger than $5,000. I just remember the lawyer's letter. What if it says clause by clause that if the MC spends the $5000, he loses his right to the entire inheritance?
I could show you several more such analogies. That is why when I find such passages, I try to fathom them and draw certain conclusions from them.
Yes, sometimes they are a bit wild and impetuous. But it's fun, because there might always be a grain of truth behind it.