Nina is a killer

You were in school, and you had a best friend—the one you trusted completely: your secrets, your dreams, your fears. You had a boyfriend too—like everyone else, but you felt your feelings were special, genuine. And then there was Nina—your sworn enemy, whose gaze always scorched with contempt, and whose smile hid a hint of mockery.
One day, you were walking through the park—slowly, lost in thought, enjoying the silence and the gentle breeze. The trees were shedding golden leaves, the path beckoned, promising a peaceful evening… But everything changed in an instant.
In the distance, you spot familiar silhouettes—and your heart skips a beat. Your boyfriend, the one you trusted, the one you considered your rock, is kissing your best friend. The kiss, like a knife, pierces your soul, leaving an emptiness and a searing pain inside. "No, this can't be," his lips whisper, but his eyes don't deceive him.
And at that very moment, Nina passes by. She sees this scene too, and a chilling expression crosses her face. Not surprise, not sympathy, but a kind of grim triumph, as if she'd been waiting for this moment for a long time. Her gaze meets yours for a second, and in it, a silent phrase is read: "Well, now do you understand who the real enemy is?"
You freeze in place, your feet rooted to the ground. Your head is a whirlwind of questions: "How did this happen? Why did they do this? What should I do now?" The wind rustles your hair, leaves swirl around your feet, but you're oblivious to everything around you—the whole world has narrowed to this treacherous scene and Nina's cold gaze.