Given the following context:

The movie opens with Isabella Ford in a pathetic state, traveling alone from Selmouth to Addisford on foot although she will be having a baby in a short while. In a deserted cabin on the way, she gives birth to a stillborn baby. She buries it and continues her journey to Addisford. She arrives there late in the evening and meets Ben Wainwright, the lamplighter at Addisford. He asks her about herself and if she has any relatives in Addisford. Bella replies that she does not have any and she came looking for a man by the name of Arch Wilson. Ben does not know him and seeing her plight, takes her to his house. He tells his wife to get Bella washed up. Bella, now clean and dry, sits at the dinner table while Ben introduces his family. Ben has three children. Matty, Con and Jedd. Matty, the youngest, is a shoemaker, Jedd is a soldier, and Con does not have a specific profession. He does the household chores and helps his parents around. Bella is unable to eat anything during the dinner, starts crying, and faints when she stands up to go to bed.
Mrs. Wainwright puts Bella to bed and feeds her some soup after a while. Bella refuses to have more and falls asleep. She wakes up in the midnight and remembers the intimate moments with her lover, Arch. She falls asleep again and wakes up in the morning. From the window, she sees Mr and Mrs. Wainwright seeing off Jedd, who is going back to the army. After Jedd is gone, Bella prepares to leave. Mrs. Wainwright gives Bella her daughter's coat and tells her that she died of rheumatic fever. She asks about Bella's family and learns that she has nowhere to go. She tells her that she can stay and she will have to do her share of household work, if she chooses to stay. She also suggests she fetch leather from the factory for the shoes. Bella agrees to stay.

answer the following question:

How did the shoemaker's sister die? 

rheumatic fever