How did Sandy know?
A poignant point to the movie is that Mary goes off to fight in the Spanish civil war on the wrong side, fighting for Franco while her brother was fighting for the republicans. The implication seems to be pretty clear, that she was such a confused little idiot that she didn't even realize she had joined the wrong side.
But it is *Sandy* who points this out. How did *Sandy* know that the brother was fighting for the republicans? I don't see any way that Sandy could have known other than Mary telling her. But that would mean that Mary *did* know.
Can anyone make sense of this?