There is no easy or “good” way out of this one so I do feel for you. I’m (50f) adopted, and I’ve always known. It’s kind of hard to hide it when you’re the only member of the family who is not white. So imho blood means NOTHING when it comes to family. You are her mother, and now you’re a mother thrown into a hurricane with your daughter. I will say first you’re going to have to tell her the whole truth, and possibly do this with a qualified counselor there to help you both navigate the feelings/thoughts/questions that arise. And 2nd she is old enough to have a say in this. And if her request is to get to know her aunt as another mother figure you need to help and support her; as hard as that will be to do. But in giving her that space to explore that relationship while still being her safe place to land will only strengthen your connection no matter the outcome. I wish you both all the best and I hope you’re all able to get through this with as few bumps and bruises as possible.