The Old Woman lives for her husband. She supports the Old Man in every way. Throughout the play, we see her scurrying around doing his bidding. She greets the invisible guests, drags chairs, and sells programs and Eskimo pies all to aid her husband in the delivery of his great message.
One of the most telling moments is when the Old Woman literally begins to echo her husband. She does this all through his long speech to the Emperor and when he addresses the crowd. This echoing shows how in many ways the Old Woman's whole purpose in life seems to be to support her husband.
The only time the Old Woman seems to veer from her husband in any way is when she gets super flirtatious with the invisible Photo-engraver. But even this seems aimed at getting her husband's attention as he professes his love to Belle. Yes, in many ways it seems her life is just a reverberation of the Old Man's.
Much like her husband, the Old Woman tries to escape from the boring senselessness of her existence through make-believe. At the beginning of the play, she begs the Old Man to play pretend and to entertain her with the same old story she's heard a million times.
Later on, the Old Woman tells a story about her son that could be seen as quite revealing. She says her son was disturbed one day when he thought the streets were full of dead baby birds. She tried to reassure her son that there were no dead birds, that they were all happy and singing in the trees. You could interpret this whole story as the Old Woman trying to shield her son from the reality of death. Rather than facing its existence with her son, she chose to try to hide in a pleasant fantasy, which caused her son to abandon her.
Notice also how eagerly the Old Woman takes part in the whole invisible guest/great message scenario. If we go with the theory that the old couple is just making this all up, it's a pretty massive example of the Old Woman's penchant for escapism. Not only does she spend all day dragging chairs around for imaginary people; ultimately she gets so lost in the fantasy that she ends up taking her own life.
The Old Woman's suicide brings us back to the idea that she lives her life only for her husband. In the end, the Old Woman kills herself not because she has fulfilled her life's dream, but because her husband has. Now that his purpose has been accomplished, she feels hers has as well. In the end it seems that even in her fantasy life the Old Woman is totally wrapped up in her husband.