I'm curious. What version of Android is your mother using on her G2?
I ask because I'm using a Samsung GS 4, and I'm having a similar problem only since upgrading to Lollipop 5.0.1. The notification icons on the left side of the status bar spontaneously disappear. The icons on the right side, such as battery, time, signal strength, etc., remain visible. Transient notification icons such as email or messaging cannot be seen when this happens. However, when I pull down from the top of the screen, all notification notices will be visible, but the status bar is still empty. A reboot will bring the missing icons back.
I've not seen many comments about this particular problem. I got to thinking that a specific app may be at fault, but can't be sure which one. I've tried uninstalling selected apps that tend to have notifications populating this part of the status bar, but haven't found the guilty party yet. Have you found the source of the problem since the original post?