Helen and Jane become fast friends after they meet on the orphanage playground. Jane has no friends, and Helen is absorbed in her book and attracts the attention of the younger Jane. Helen is not destined to be Jane's friend for long, however, as she has a consumptive cough (we call it tuberculosis today).
Jane and Helen are actually opposites during their short-lived friendship. Helen is patient and forgiving and humble; she conducts herself in a moral and upright manner, even when she is treated unfairly or unkindly. Jane is none of those things as a young girl, at least in part because of the events and treatment which sent her to the orphanage.
However, Jane does learn from her friend Helen and becomes much more like her as the story progresses. Jane is still much more spirited (feisty, sassy) than Helen ever was, but over time she learns to be much more tolerant and forgiving of the flaws and foibles of others. By the end of the novel--and especially during her self-imposed exile from Mr. Rochester and Thornfield--Jane learns to be more like her dearest childhood friend.