Rights of relatives over one's income

As a wife and as a physician, I have chosen to work and earn. My husband (also a physician) also earns for our immediate family but my mother (a widow) and other relatives have placed responsibilities upon me. I have partly supported my sister''s educational expenses and now am saving for her wedding. I have partially supported my aunt''s medical expenses (she has cirrhosis of the liver) and routinely provide medical consultation and dialogue with her doctors (my part involves making multiple international phone calls for weeks and weeks). Now my aunt wants to proceed with a liver transplant and everyone is looking towards me for financial support and to provide lodging for my aunt''s family. This expense is too large for me to bear.

The pressure from the extended family that I am facing is very frustrating. I feel as though I have done enough for my aunt. My mother routinely reminds me that Allah swt made me into a doctor to help our family and that a third of my income should be spent on my extended family (including my mother, aunt, etc). What are my financial obligations towards my aunt (her husband is still alive and provides for her)? If I do not support my aunt fully in this matter, is this reason for Allah swt to withdraw the income He has blessed me with?