Probably meant her cell phone, acting as a GPS through the cell towers, was down.
Very few people use a dedicated GPS anymore. The vast majority use the cell phones, which also act as a personal tracker, allowing anyone with access to the cell information to know exactly where your phone has been, and for how long.
Putting the cell phone in airplane mode does not stop the tracking. It just shuts off the phone from reporting to the cell network. Once the cell phone is connected back to the network, it uploads all the GPS location data of where the phone has been to fill in the gaps of when it was disconnected from reporting to the network.
Only a Faraday cage, which stops the phone from receiving location data, stops the phone from keeping track of its location.
$10 Faraday bag or any small metal box works fine.