Huang Zi cried because she saw Allen's past of how he had suffered from his illness since he was very young.
Huang Zi also had seen how the Williams family struggled to find a cure for Allen. They've searched the entire world, gathered all the experts in Medicine and herbalists, and did a lot of research. However, they still failed to create an effective medicine for Allen.
Allen already underwent chemotherapy and STEM CELL therapy after. But it would not help to prolong Allen's life.
The Earth has slow progress in advanced technology and curing disease. They were behind compared to other civilizations across the universe.
Just like the world where she came from. Even though many were weak; however, every being possessed power, allowing them to use it for daily work and do extraordinary things.