Your sister is very lucky to have you, even if she does not realize it right now. You are in a very difficult situation. No one likes seeing people they love make choices that can lead them to harm. You’ve already done a great deal for her by talking with her directly, and by talking to your parents. Unfortunately, there is not very much more you can do. The more you focus on her eating, the more she might become angry with you, and perhaps the more she will eat.
Perhaps you can try to find another way to go about helping her. For example, perhaps you can get her involved in some fun physical activities. Perhaps your parents would be willing to support this, since people with diabetes always do better if they are physically active. The fact that she may lose weight in the process would be a bonus, but not the focus of the activity.
Good luck in your efforts to care for your sister. No matter what, support and love her. She’ll need you later when she’s ready to take charge of her body.
JWB
[Editor’s comment: Perhaps, you can approach your sister and parents with the idea of going to her next diabetes team visit. You can use the excuse that you’d like to learn more. If they go for it, maybe you could persuade your sister to visit to visit with the dietitian. Tell her that you’d like to learn more about healthy eating and go on a meal plan with her.
SS]