Take your silly assumption to its logical end and it’s supposedly reasonable for the occifer to arrest anyone else in view at the time he’s arresting somebody else — because after all those other persons might have guns at the ready.
The woman moved away when asked to. Why was that not sufficient?
Again, how do you know the woman’s real intent?
The only thing the officer knows is that she came within 6 feet. Beyond that, her intent could be anything and the cop has to assume the possible worst.
The officer, by training, has to assume that nobody is harmless and that things can go south really fast. He’s in no position to assume that things are going to be all right.