How can I help someone that doesn't want to be helped?

recently began work as a wellness practitioner, my knowledge gives me a way of keeping people healthy without drugs of surgery. I treated a person today and she brought up the subject of her daughter (who is diabetic; type 1) I offered her a diet to help, she refused and said that it was hard enough for her daughter when all her friends eat chocolate and sweet foods around her. The hospital is rubbish as the food it recommends is not helping. The lady doesn't want my help for her daughter even tho I have offered her evidence. I feel terrible as I feel she is hurting her daughters health but can't do anything. I have all this knowledge and I can help far more than a medical doctor or nutritionist. But people dont want to listen, how can I placate myself?