I don't see any reason for Cassie to figure out that Ennis is gay. Not because she is too dumb to figure it out. But, a man being gay just wasn't something that she would probably consider until the evidence was in front of her face. He wasn't seeing any other men except for Jack, and they had their fishing trips "cover story". The society at large assumes that men are straight until proven otherwise. Maybe thru the years, she thought about Ennis, and maybe she wondered later on after she married Carl.
I liked Cassie, just like I liked Alma, and I felt for her dissapointment in Ennis, just like I felt for Alma's broken heart. When I see that scene in the bus stop, I wanted Cassie to grab that plate of pie and rub it in Ennis's face, of course that is consistent with my feelings in the Thanksgiving kitchen scene, I wanted Alma to break that plate over Ennis's head. Those women were way too nice to Ennis.
