Even Rasoolullah salallahu alayhi wa sallam was victim of black magic so what can we say? This world is a place of test - the person who did the black magic failed the test, your aunt had patience and took upon the means to get cured, she is showing signs of passing the test insha'Allah if she keeps at it. On day of judgement people who endure such health difficulties in this dunya are going to get a huge mountains worth of reward for it. When the other people see the reward they will wish that in the dunya their skin was cut with scissors.