like some else said, "do not
punish her for being open with you!!" by being pushy, you will only create more stress/ feeling of helplessness in her that she can't get help. in reality you should get her to talk with a psychologist/therapist that will help find the root of the problem and give her step by step advice on how to recover. after that just be as supportive as you can. remind her that she is beutiful and shit on the reg.
(however don't over do the positive reinforcement because if she picks up on that, it can also possibly create feelings of helplessness, she may start to think that you don't really think that, but that you keep saying that to make her feel better.)
the biggest thing is be supportive and get her to professional help.