Oh, I am well aware that safe words can be forgotten in the heat of the moment. In fact I have accepted a call of "safeword" as a safe word, I am also well aware (as hopefully most of us are) that sometimes a sub will withhold the safe word out of pride or duty, and they can even be in a place where safe words no longer exist.

As to the question of how to tell, well it's body language. All of the things you described along with a dozen others. If you pay attention you don't need the safe word. I consider the use of a safe word to be a failing on my part. Of course if she is just refusing to beg for mercy out of pride. I am happy to allow her to test her will.

That said, I also see the words tossed about a lot. It almost seems that people want to rely on the safeword instead of trying to really communicate. Make more words, use a stoplight for communication during play. The safe word should only be for emergencies. It must be honored and all play must stop.

Just another opinion
Bear