Why did women become involved in charity work during the nineteenth century?

There were probably many reasons, but one was the Humanist movement. During the 1200's to 1700's, the only people who mattered were Royalty. Common people were literally no more highly regarded than pigs or cattle. There was no sense that they deserved decent lives, with food, clothing and shelter. It was not supposed (by the educated and literate) that they were capable of feeling pain. If they were sick or in agony, it was assumed to be God's will. During the Humanist movement, women, children, the poor and others who had previously been thought to be sub-human began to be recognized as viable people with real feelings, worthy of a minimum standard of existance. So, the wealthiest women gradually began to help the disadvantaged. This was reflected in the art of the period, which often had women, laborers or children as subjects, unlike previous centuries, when art focused almost entirely on religious subjects, or portraits of the rich & famous.