If it was on an extension cord, then yes, that’s what did it. Should have still blown the breaker if there was one. In that sort of situation the breaker probably won’t save the person in the tub, just the people that have to fish them out later.
No it would not blow any breaker the current needed to kill her was a fraction of an amp. Not 15- 20 amps. The idea that if you throw an extension cord in water then it will spark and blow a “Fuse” is pure Hollywood. Completely fictional. Only a fraction of an amp is produced by that procedure.
But yes extension cords can be bad in this situation because they are sometimes designed so that the charger can be plugged in with two main prongs reversed. This allows what is supposed to be the neutral side of the charger to become hot.