Switching addictions

It is not uncommon for addicts to switch addictions.  The smoker who begins eating compulsively.  The alcoholic who begins taking prescription medication.  It underscores the statement addiction is addiction.  If your sister is a compulsive eater, by definition she is using food and eating to deal with emotions.  The eating behavior is causing a problem with her physical health, personal life or occupational functioning.  Switching addictions or finding trying to alter addictive behaviors is how an addict rationalizes that they are in control of their behavior.  With eating addictions, using laxatives, cutting out food groups, only eating at certain times, creating a ritual around the eating behavior are all ways to avoid addressing the real problem.

You instinctively know that drinking beer instead of compulsive eating isn't a way to manage disordered eating behaviors.  Once someone starts drinking to manage feelings instead of eating to manage feelings they could potentially begin to drink more and become addicted.

It is unfortunate that your sister isn’t reaching out for help through overeaters anonymous, self-help groups or therapy.  As difficult as it is to watch you need to remember that you didn’t cause her addiction.  You can’t cure it or control it.  But you can contribute to it if you enable her.