Hello, my name is Rusty. Someone turned off her location services. You'll have to get your hands on the phone to turn it back on. Go to settings, then location services. At the bottom, tap share my location. You'll see the button to turn on the location sharing. When you turn that on, her location will show up.
That feature is there for when you don't want to be tracked. When you turn off your location services, it's impossible to find the location of that phone.
Hello, my name is***** an iPhone sits for a while, it will pause the location until she is moving again. You may want to turn off her location and turn it back on if it is not working properly.
If that doesn't offer a permanent solution, do a factory reset on the phone through iTunes. That should fix it for good.