I'm not for sure but...it sounds to me like the app knows that the Xbox and tv aren't mobile devices and therefore should only be connected while on the subscribers home network.
The TWC TV application provides limited access to programming when your device (whether mobile phone, computer, gaming console, etc) is connecting to the internet through any other internet connection than the home network. If your mom would like to access programming from any premium network (HBO, Showtime, Starz, etc) that she is currently subscribed to, she can do so outside of the home while connected to any network. The following LINK will provide you with detailed information regarding the application.
TWC Community Forum Moderator