Until you call an electrician, all I can think of is to plug something in and do the on/off test. You said you aren’t able to find anything to plug in there, but I don’t understand what you mean. A lamp, TV, toaster, phone charger, alarm clock, radio, microwave, any of those would work to test with to see if the outlet has power when switching off the breakers. Unless she has nothing else plugged in throughout the entire house then I would just do that, it’s by far the easiest way to test.
Until you call an electrician, all I can think of is to plug something in and do the on/off test. You said you aren’t able to find anything to plug in there, but I don’t understand what you mean. A lamp, TV, toaster, phone charger, alarm clock, radio, microwave, any of those would work to test with to see if the outlet has power when switching off the breakers. Unless she has nothing else plugged in throughout the entire house then I would just do that, it’s by far the easiest way to test.