I hope you enjoy your visit. When exactly are you coming; it would be great if you could meet up with some of us locals.
It's a shame your G/F isn't OK with it because you are going to be in one of the safest states to OC. You're unlikely to be bothered by and police or citizens, other than someone asking what kind of gun that is and trying to compare notes. You'll certainly be fine with your Washington CWL if you choose to conceal.