Everyone makes mistakes. Be patient with yourself and with your loved one or friend. Their eating disorder has become their friend and they will not let go of it all at once. As they learn additional coping skills via their therapy, they will gradually say goodbye to the eating disorder. During this time, when emotions are running high, it is important for you to have a place to discharge your emotions and receive support.
Recovery is a process and takes time.
There will be many setbacks along the way. You will need to learn how to manage yourself in a relationship to the person with the eating disorder. A lot of negative affect only sabotages recovery. Particularly important is your detachment that comes from understanding the eating disorder voice verses the healthy recovery voice. By reading you will be able to love, support, and empathize rather than blame, chastise, and threaten.