What should i do????shes cutting herself?

in my physcology cl there is this girl who sit next to me. since september i have noticed that she has cuts on her wrist.there are about 3-6 cuts normally. the longest ive noticed her wrist free of cuts were for a week. for the past 2 weeks her wrists have been covered in cuts. shes now got about 10 -14. she not a shy girl but shes not too outspoken either. she looks happy. but one day i was talking to her and she told me that she hates people who judge. she said that theres alot more to a pearson than the outside and she said that she finds it amazing that a pearson can hide so much pain theyre feeling just by smilling. today at the end of cl right before the bell she was sitting on her chair and out of now where she started crying. it wasnt obvious no one else but me noticed. ( i only noticed b/c i keep and eye on her b/c i dont want her to hurt herself to badly) i go to her and give her a hug and i say whatever it is u can tell me. i mean like come on i sit right next to u. she said that its complicated and that i would understand. everything ive been witnessing with her has really been worrying me. what can i do to help her. without telling and adult or guidance. i want to help her.