It is so hard to watch someone you care about going through something like an eating disorder. I recommend just fully showing your girlfriend that you are here for her and that she can talk to you anytime. Let her vent and get everything out before you offer advice. She probably really needs someone to listen to her, more than she needs anything else. Never issue threats, like if you don't eat, I'll be mad or I will not stay with you. Many people do that with the best of intentions that it will help their friend, but it just makes them feel more isolated and want to do the dangerous activities even more due to stress. Distract her, make her feel loved, and listen to her. Also, ask her ways that you can help. Maybe she has something specific in mind. I know she will appreciate your support during this difficult time.
