My grandma told me that her chest feel pain in the night after she ate her medicine (diabetes medicine / chinese medicine) may I know why?

Have it evaluated. A person with chest pain needs to be evaluated and treated appropriately. Multiple possible causes may be: heart attack, esophageal reflux, anxiety, musculoskeletal, pneumonia, pulmonary embolus, and aortic dissection. Have it evaluated right away to prevent potential serious complications.