YTA. I hope that any adoption agency with an drop of ethics will recognize how bad it is for you to adopt. You are treating your niece like an object. You do not see her as a person who has lost her parents. Your older sister has been taking care of her for the past 5 years. Get help because you aren’t in the right state of mind to have kids let alone adopt. They are not status symbols or pets. Kids have feelings, trauma, and have their own free will. They are not an extension of yourself where you can play doll and control their life. If you want something to dress up and control get a god damn doll. Don’t for the love of god give another kid more trauma for your selfish desires. Really reflect on yourself how you view kids. Kids are not support animals that give you unconditionally love.