I disagree.
When I try to look at the screenwriters’ choices, it reinforces my belief that Junior knew.
I often wonder about the storytellers’ motivations for choosing this-or-that dialogue. Is it a part of the plot, or is it character development, or is it a red herring, or is it simply a mistake; an extraneous bit that never managed to get edited out but in the end contributes nothing.
In this film, nearly every detail seems to contribute something of value.
And what would be the value of Junior being jealous of Cassie?
It isn’t important to the story.
She *is* jealous, of course, but that’s not a valuable piece of the plot here; she’s portrayed as such simply because it’s fitting—she’s not getting private time with her father.
But to me the point of the scene is to show her connection to him. She observes him quietly. She's concerned, and she's wondering. She strongly suspects the truth about him, even though he's not the 'type' at all.
Why can't the scene be simply about showing how Junior is a daddy's girl? We hadn't really seen that up until that scene. And that despite being a daddy's girl, she's also Alma's daughter picking up such phrases as 'not the marrying kind' and while that can be a very very 1960's small town euphemism for gay, there are plenty of cowboys who didn't and don't marry. That doesn't automatically make them gay or in the closet. Otherwise as a single straight woman who isn't interested in marrying, I might be called a lesbian since I don't seem to be the 'marrying kind'.
Or more importantly, perhaps the scene is there to show how Cassie is actually
trying to get Ennis to marry her, that she is serious about him, very much in love. That would make her pain more real in the scene in the bus stop diner when Cassie and Carl come in and she spots Ennis. And it's more reasonable that a scene that deals with an emotional issue like marriage would occur between two women - Cassie and Junior - than a scene where Cassie is trying to get the taciturn Ennis to open up about why he won't marry her.
There are many reasons why that that scene is there. Doesn't
have to be the setup for the end. The ending is more about Ennis anyway than Junior, IMO. She doesn't
have to have some sort of epiphany about her father to make the scene work. She can be just a simple girl happy that her daddy understands her love and is finally making time for her, no matter what.
That scene is Ang's idea of a happy ending for Ennis. In the short story, his children are such nonentities they are only mentioned in passing, not actually part of the story, so there is not even a hint that Ennis' kids have a clue. So I tend to think of the ending scene as more about Ennis' growth than any realization by Junior.