Man Is Worried His 650 lb. Sister Is Slowly Dying and Won’t Do Anything About It

Ultimately, as one commenter put it, “I think this is beyond Reddit’s pay grade and you need a professional therapist / intervention specialist.” Even if she won’t see a therapist, OP should see one to help preserve his own mental health. 

A therapist could refer him to the best course of action, but most importantly, they could help him navigate his feelings and make sure he’s in the healthiest space possible to help his sister when she decides to accept it.