How old are you? So there was no one able to take care of your grandmother, and you were her full time caregiver 24/7. So couldn’t go to school or work either and “had” to care for her? She had no siblings, children to look after her, only a grandchild?
Show reports from doctors and appointments that she needed around the clock care. Include family documentation that she had no family and explain why a grandchild was the only person who could care for her 24/7. Explain that you were not able to go to school or work because she was your responsibility.