Category talk:Missing in Action

Why is Four Seven Niner in this category? It was never referenced that she died or went missing, she just never appeared again, so why is she in this? Also, should Sister be included in this? I know that Lopez said he killed her, and I believe that he did and she's dead, due to Sarge disabling his lying protocols moments before. However, we never saw a body and it was never confirmed by Rooster Teeth, so should she be put into this category?