What can I possibly say to her?

Just know that she isn't necessarily looking for answers from you. She is just looking for support and somebody to talk to. Let her know that sometimes you won't really know what to say but, you will be there to listen to any problem/emotion that she has and support her. Encourage her to talk to her parents about it too. That should really help if she can understand their feelings and, if she's still confused, maybe you can try to understand and help her out. Hope this helps!