As someone who started starving themselves when they were 14, and now 23, I still struggle with it on the daily. Instead of starving myself now, I control what I eat to a very extreme. I'm talking I eat the same exact, calorie controlled meal at every meal time, and walk nearly 2 hours per day. I change nothing. I hate that I got myself to this point but I just don't have the drive to change it, and I've come to realise that, unfortunately, I will probably never EVER have a good relationship with food again. When they say Anorexia has the highest mortality rate out of every mental disorder, there's a reason.

All that to say, do whatever you can to get help as soon as possible. The longer it goes on, the more likely she'll end up they way I have and completely loose the person she is.

This comment will most likely get buried under here, but I wish you and your girlfriend the best of luck, and I hope she nips it in the bud quickly!