Her weapons consciousness is taking over. I think the song was propaganda. They said they always played it. It was mentioned in the first episode when they went to the mall. I don't think he kills her because there are two episodes left.
A moment's respite - the brief happiness; for as long as it lasted, it was memorable and great. I am glad that Saikano managed to at least place a moment of happiness, even if it may come before an endless tragedy.