Usually, people don’t raise their voices against the sexual harassment faced in their families. But this is a very serious matter. You can’t just let this matter slip out. You have to raise your voice against this. You definitely need to inform your parents about this. But, the problem is that they might not believe you. So, you need to collect as much evidence against your aunt. It can be any recorded audio or video that can prove that you are stating the truth.
But, you need to talk to your parents as soon as possible. She might continue to harass you further. So, better try not to be close to her as much as possible. Then after collecting the evidence you can stand against her.