What are the responsibilities of a wife to her father’s family?

I am doing private service and within income limit Alhamdulillah. By the grace of Allah, we are well. In my family, we have no kids yet; only me and my wife. Recently, my wife has completed her master degree in accounting and wants to join in service for support her parents’ family; because she has three sisters are studying in different class and her father retired from service and has no son to take the responsibility as income source. Her father is also facing problems to maintain educational expenses of the daughters and living cost of the family. Please also note that I have not enough income to provide support my father-in-laws. In this state, my wife wants to do jobs for her parents’ family but I do not like job for my wife due to veil (purdah), today’s social working environment and my family responsibility. According to Islamic law, what are responsibilities of my wife to her father’s family? And can she do job? What is my responsibility right now for the above?