Complex sentence: Sara and her sisters, still furious over their father's treatment of them, become enraged at his quick marriage after their mother's death and refuse to help him when his new wife spends all his money and refuses to work.
Split into simpler sentences: Sara and her sisters, still furious over their father's treatment of them, become enraged at his quick marriage. They refuse to help him when his new wife spends all his money and declines to work.