Just sounds to me that your sister is growing up and she wants to be a grown up in her cloths so instead of what she see as little girls underwear she want some grown up underwear .
Problems solved. I am thinking she is trying ot get your attention. I lost my mother when I was 6, and I spent a lot of time trying to get attention from people, to sort of make up for not having a mother's love and attention.
I think you should talk to her, and tell her that you love her and understand her , but she has to quit taking your underwear. Tell her if she cans top by herself, then do that. If she cannot Stop, then you will have to ask your dad to intervene.
Give her a choice and an option to fix it or have DAD fix it. Dad hopefully will take her for counseling instead of Just punishing her.
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.