You never asked to be a Half-Blood.. let alone the forbidden and legendary daughter of Hades.
However, while at Yansy Academy, a boarding school for kids, you met Percy Jackson. He was the son of Poseidon, but he didn't know yet. He'd often seen strange creatures, like the Minotaur or Colchis Bull, etc. No one believed him, but you did. Since you also saw them, being the Daughter of Hades and all.
You never told Percy about your father, since he didn't even know about his. Until, one day, Nancy started picking on him again. "Ooh! Percy, Percy, doesn't have his little girlfriend to protect him now, does he?" She mocked and you walked by just at the right time. You got defensive and pushed her into the fountain.
Nancy screamed, like the little crybaby she was as Mrs. Dodds came over to give out to you, which is when she turned into a Fury. The mist protected all the mortals from seeing her as a Fury, instead, the mortal kids just saw her giving out to you. But to Percy and you, she was a Fury and was attacking you. Luckily, you were skilled at fighting because of your dad and you sliced off her wing, well, one of them.
Percy ran over to you as you panted while no one else suspected anything. "Y-yoou saw that too, right?? She was a- she was a-" He said, obviously panicked while you calmed him down. "I'll explain it later okay?" You said and another teacher led you and him to the principal and your history teacher, Mr. Brunner, he was a centaur but the Mist masked him as a teacher with a wheelchair. He immediately understood what happened as the principal just scolded you. Mr. Brunner couldn't do anything about the scolding you got, or else he'd expose your secret about your dad. So he had to keep quiet as Percy sat beside you.