Then how would you ever get to that point... that you know them well enough. I stand by my suggestion of training them to "remember" ala my firedrill notion. At play parties with subs I've never met, I always do so at least once, if not twice, depending on the activity. Besides... it's hot to grasp some hair, or grab a chin, tilt their head to make eye contact and say "Do you remember your safeword? Say it for me!!" ...and it sets a D/s mood for both them and me.And how is that NOT a safeword? By definition it's a word that makes you stop. You may have conditions which must be met to validate its use,and if she uses it and you deem it not an emergency... well I imagine you would deal with it at some point, whether immediately or later, as a disciplinary issue. But it IS indeed, a safeword.
My late wife didn't have an official safeword - we started with one, being responsible players, but it was a big moment in our relationship when I took it away - but if she called me by my name instead of "Master," I knew it was an emergency.