Today, after being afk, my wife checked her settings again, only this time the options for "Display both pet hotbar and hotbar 1" and "Display only hotbar 1" were both grayed out.

I'm attaching an image here, but I must apologize for it's size. Her screen resolution is 4k, and when trying to change resolution to shrink the screen capture, the buttons were no longer grayed out.

Image Here.

edit: Just to clarify, she did not change classes, move anywhere, or actually change anything beyond opening and closing the settings window.