Your friend is lucky to have someone like you in her life that wants to support her through this difficult time. It can feel so lonely going through something like this because often the survivor can feel guilty for struggling so much.
*the most important thing is to listen.
Dont say things like get over it, you have to put this behind you etc. Her feelings are valid and they need to processed and worked through, telling someone to just get over them makes them feel like they are not being listened to and like they are a burden.
*its important that she has a support network while going through this and agencies like the rape crisis helplines or rainn can help. So it might be helpful to google agencies in your country which could help her through this time.
*remind her that she won't always feel this way and that there is no one way to deal with this kind of situation, and encourage her to seek help of she needs it but don't push.
*take care of yourself too and know that you dont have to come with the right words because there really isnt any and your actions of just being there speaks louder and says more than any words could.