It doesn’t matter how long refueling takes. Why can’t one use the bathroom during this time? What is the danger?
There is none. The fuel is pumped into the wings. I was a "ramp agent" for the airlines many years ago. The "ramp agent" job entailed handling luggage on and off the plane, fueling the aircraft, replenishing the water supply and emptying the "lavs" (as they were called) among other things.
So fueling the plane has zero to do with the toilets on board the aircraft. This is just another symptom of the heavily regulated society in which we live.
That said, how does one handle having to urinate and not having a proper place to go? Not that there's any excuse for having to go as soon as you get on the plane. Don't people have the common sense to use the terminal restroom before boarding the plane? I'm thinking this particular woman might have been spending time at the airport bar before boarding.