I suppose that there are a couple of answers to this question depending on when in the story the question is asking about. If this question is probing early elements of the story, then the same thing happens to Mother Shipton as happens to the other outcasts of the town. Mother Shipton has been evicted from the town for her morally ambiguous occupation. She is a prostitute, and the town wants to get rid of people that are "improper."
It had lately suffered the loss of several thousand dollars, two valuable horses, and a prominent citizen. It was experiencing a spasm of virtuous reaction, quite as lawless and ungovernable as any of the acts that had provoked it. A secret committee had determined to rid the town of all improper persons.
Mother Shipton shares her eviction with Mr. Oakhurst, Duchess, and Uncle Billy. The goal for the group is to get to a camp named Sandy Bar. Unfortunately, the group decides to make camp far too early in the day, and they are snowed in as a result. The group can't begin traveling again, and their food supplies dwindle quickly. Mother Shipton, Oakhurst, and Duchess all die as a result. I would like to make it clear that Mother Shipton did her best to keep the other outcasts alive by giving up her portion of food for the benefit of the other outcasts.