Also, what you are saying is that we must believe it because that's what DPC wrote? I don't buy that. As I've stated before the burden is upon the author to make their story something that a reasonable person CAN believe, and on this DPC has failed miserably.
no, I'm not saying that.
I think it is a premise that has not been told to us but of which only clues have been given to us. I don't think it is fundamental to the story, the salient fact is that Maya's father was the decisive obstacle in their relationship, how he did it is not clear.
in the same way as the relationship between Neil and Linette's family is unclear, or why Rusty and Jill's date went wrong or what is in Bella and her husband's past. these are all stories that have been mentioned to us, with no real explanation. some maybe will be taken into consideration (that of Bella I would take it for granted) others could remain mere hints.
maybe in the next chapter there could be a flashback to this, but I don't think it essential.
the idea I got is that for Maya's father the problem is Josy (which in fact is the goal of the ultimatum to his daughter) and not the homosexuality itself. he probably considers that Josy has plagiarized his daughter and dragged her "into sin". so more than physically preventing his daughter from communicating with Josy (for me impossible nowadays), he prevented her psychologically, questioning their story, the sincerity of their feelings. this would also explain the harsh tone of their phone calls with Maya pressed by her father and Josy unable to answer Maya's expectations for her problems with college acceptance