The only way this could happen is if she was plugging in the phone to the outlet with dripping wet hands. The outlet would have to be without a GFCI installed. Her feet were wet completing the circuit.
Regardless of what the headline is implying, the cellphone did not electrocute her, the outlet did. A cellphone doesn't have even one hundredth of the amount of power it takes to kill someone.
This should be an alert to everyone to check your outlets in the bathroom, over the sink in the kitchen, and generally anywhere there is water, and make sure they are GFCI outlets. It could save a life.