The only thing, I see, wrong with incest is offspring. So if you don't mind, I say, go for it. Or if you want her to stop then just lay it plainly on the table.
Tell her that you're her brother, it's wrong or some sh*t and to leave you the f*ck alone. If it doesn't work try to distance yourself from her. Or just tell your parents.
They'll talk to her about it.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.