In chapter one, Jane's aunt explains to her that she is being ejected from the drawing-room because of her quiet, unsociable nature. Her aunt assumes that her quietness means that she is an unhappy, discontent child:
She regretted to be under the necessity of keeping me at a distance . . . she really must exclude me from privileges intended only for contented, happy little children. (ch. 1)
Irony is when something is just the opposite of what is expected or actually occurring. In this situation, her aunt's comment is ironic because Jane is generally a happy, content child. A page later, the narrator explains:
With Bewick [a book] on my knee, I was then happy: happy at least in my way. I feared nothing but interruption, and that came too soon. (ch. 1)
Jane reveals that she is happier when she is alone, quietly reading, than she would be in a room full of people. She appreciates her quiet moments where she can think, learn, and be introspective. When she is with her cousins and aunt, she faces judgment and even abuse (from her cousin John). When she is alone, she can let her imagination run wild.
Jane's aunt believes that it is a punishment for Jane to have to be by herself, without the company of her cousins in their drawing room, which is like a living room or common area. What she does not realize is that Jane is most content when she gets to be on her own. It is ironic that her aunt's supposed "punishment" of not getting to stay in the drawing room is actually something that Jane enjoys and appreciates.