She's vicious.
Finn can honestly say that he's been scared of her before. With her long hair whipping him, a savage expression on her face and that look in her eye, she sometimes seems like an animal.
"Do you love me?" He'll ask, and she'll just laugh, shaking her hair at him.
"This is sex, Finnocence. Sex isn't love."
Her nails claw down his back, and as she screams out in pleasure, he knows he'll have scars there for weeks.
He sometimes thinks that she could eat a boy like him for breakfast, then rinse her mouth and go about her day. He accidentally says it out loud once, and she gives him the strangest look before telling him to "shut up, because you're ruining the mood".
Finn doesn't know it, but he means something to Santana. Something more than mindless, meaningless, loveless sex. She doesn't know what it is at first, but she eventually recognises the butterflies. She knows she doesn't mean anything to him, though, and she knows it because he's always staring at Rachel, and it's not like he hasn't said that bitch's name while he was with Santana.
He gets more and more distant, and Santana can tell he's pining. She scratches and bites and screams, trying to pull him back, trying to stop drowning. She needs his attention, she's craving it. But there's always fucking Rachel, ready to take Finn back, and Finn's still in love with her. Santana can tell.
One day, Finn doesn't show up at her house, and when Santana gets to Finn's house, it's Rachel that opens the door. Rachel looks embarrassed (the hobbit, embarrassed for her?), and Santana mumbles something incoherent before running away. When Finn and Rachel are hand in hand at school the next day, she breaks down and sobs in Brittany's arms.
"I just think that people, they suck, you know?" she cries and cries until it's all gone.
And when it is? She makes a vow.
Santana Lopez is going to get Finn Hudson back.