You have the choice to treat your parents in any manner you deem appropriate short of physical and mental abuse but ...if i were you, I'd be careful about the observations your girlfriend is front seat for because she might start wondering if she is getting the same treatment.....like little white lies, contrived excuses, word play and experiments with deeply held beliefs.

Now if she doesn't seem to be bothered by any of this.......you might find yourself taking a DNA test someday.