atrix hd "out of network" problem

Try having her turn the phone off and then back on to see if that will correct the service problem. Also, try having her move to a part of your home that has the best coverage. Not all rooms have the same coverage, which I'm sure you already are aware of.

If power cycling the phone does not help, I would recommend removing the battery and SIM card. Place them back in the phone and turn it on again.

I would also try turning off Data Roaming if its on, just in case that the device is picking up another operators signal.