Well if she doesn't know the person, then I don't know why you would have to tell her. No, I wouldnt, it would only hurt her feelings. I hope if you were present when this happened you set the person straight and stuck up for your girlfriend.
I would be sure in the future to safeguard her from this person, like if there happens to be a party where they may meet up, just keep your eyes and ears peeled. Serves no purpose in telling her at this point.
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.