Agree with "Kat".......
It probably is the sender.......get an estimate like Kat says......you have to drop the tank, to install......the fuel module is expensive......
Should NEVER run below 1/4 of a tank......you want that fuel pump covered with fuel....if it is not covered by the "cool" fuel, doing this repeatedly will lessen the life of that pump.....surprised she has not ruined it already, if she does it all the time.....I guess she needs to be stranded somewhere, maybe, to get the message....