I think that the best thing that you can do for your friend is to make sure that she knows that you are standing by her side. However it is equally important to take time for yourself and not to try and fix her. This is something that she has to do, the action that needs to be taken is action that she herself has to take, but she doesn't have to do it alone.
It might be a good idea to try and get her to go to some NA meetings: https://m.na.org/ And maybe you can go to one with her, but just tell her to sit back and listen out for the similarities if what people are saying and not the differences. If she likes reading, suggest that she reads the basic text: https://www.amazon.co.uk/Narcotics-Wso/dp/1557767351
And if she hates the idea of god, make sure she knows that NA Is NOT a religious programme but a spiritual one.