An interesting observation. What really pissed off Sage? After unsuccessful sex, we see how she speaks to the MC and her reaction is peaceful and supportive. She holds his hand, caresses it a little.
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She is not worried about interrupted sex, she sees that the MC feels uncomfortable and tries to support him.
Sage instantly changes his behavior when the conversation turns to their biological parents. He tries to ask Sage about her real mother. At this moment, she begins to get nervous - her face changes and her eyes begin to run. After that, she has an anger moment.
It looks like it's a very bad memory for some reason. She may have had terrible parents, but this version raises questions because Sage kept her original last name Morgan from them. If they were a terrible family, she wouldn't have done it.
The second version is that something terrible happened to her parents. Maybe they were killed, or died in some kind of disaster. And for Sage still, many years later, these memories are hard to come by, so she interrupted the conversation with a scene.