While she should obviously have stopped when asked it is an utter fallacy that mobile phones have any affect on the operation of an aircraft.
You say this. But I was on a flight last November which was attempting to land in fog and at the limit of allowable cross winds. The pilot spoke to us about the landing, from memory he was landing manually using the instruments and with ATC guidance, and I distinctly remember he asserting that he needed everyone to adhere to the mobile phone policy as it can interfere with communications. After the flight I chatted and was told pilots can sometimes pick up, in their headsets, that noise we hear when a phone is used near a radio.
I guess they routinely ask for phones to be turned off in case they have an unexpected emergency during take off and landing.