She must witness something the couple doesn't want seen. Not just cheating. Perhaps she sees the guy crying because he can't afford her ring. Perhaps she sees the girl writing a goodbye letter.
There's also a growing conversation about the impact of explicit content on mental health and relationships. Some argue that it can contribute to unrealistic expectations and unhealthy attitudes towards sex and relationships.
Unlike Western stories where the observer stays silent forever, in Pinoy storylines, the Boso always steps out. "Oo, nanonood ako. Ano ngayon?" (Yes, I was watching. So what?) This turning point shifts the power from the observed back to the observer.