In "Inglorious Basterds," why does Hans Landa bother killing Bridget von Hammersmark?

So, whenever I watch Inglorious Basterds, I'm struck by this question: Why does Landa kill Bridget von Hammersmark, and why so personally?Consider: At this point in the story, Landa is already fully intending to go along with the Basterds' plot and allow the theater to be destroyed with all the Nazi high command in it. He plays with the members of the Basterds in the lobby just to rub his power in their faces, but as long as they're willing to make a deal, he knows they're his ticket out, to a comfortable life in America.Thus, it's not as if he could reasonably be said to hate von Hammersmark for being a double agent--he's about to betray Germany himself. He clearly has no honorary allegiance to country. Does he kill her just because she's unnecessary to brokering that deal? Or because it makes it that much more of a surprise for the audience when he offers to turn against the Reich? <---- This latter point seems like the most likely filmmaking reason for him to kill her, but it's not necessarily consistent with the character.And then there's the manner of the death. Throughout the whole movie, Landa is shown to be a guy whose primary weapon is his mind. He allows the grunts and enlisted men to do his actual dirty work for him, because he's a strategist rather than a soldier. So why does he lead von Hammersmark into the theater's back room intending to physically strangle her to death? It puts him in unnecessary risk, when he could just as easily have had her taken away by the SS, as he did with Aldo and co. Is he just a psychopath who has been waiting for an opportunity to strangle a movie star? It seems rather out of character to me.In short: Killing her was unnecessary, so it had to have been something he personally wanted to do, but we're never really given a rationale or justification for it. via /r/movies http://ift.tt/2AbqW9W