Upgrade subject to access all content
The fact that Aunt Alexandra does not make Jem turn the lights back on in Chapter 15, when he shuts them off to look out undetected at the crowd gathered outside his house, primarily shows
She is not as much in control of those around her as she wants or pretends to be when she gives commands.
She actually wanted to eavesdrop as much as Jem did, either from curiosity or fear - or a mixture of both.
She has begun to respect Jem as a man of the house, and so defers to his judgment on the matter.
She is too lazy to get up and switch the lights back on herself, even though she really wants it done.
She is afraid of Atticus getting upset with her for crossing the people he cares about most, like his children and Cal.