Hi, I'd like to help you with your question.
Is your niece willing to get help? Or is she resistant? If she is willing, she can contact the local community mental health/drug and alcohol treatment facility and they can give her a list of the facilities that will help her. They will also assist her in applying for funding if she does not have insurance.
You could also assist her if she is willing to let you. You can contact the mental health/drug and alcohol facility for information.
If your niece is resistant to treatment, then there is not much you can do. She is an adult so unless she is intending on killing herself or threatens to kill someone else, she cannot be forced into treatment.
If your niece is court ordered, she can contact the court for further assistance. You could also do so, but I'm not sure they would give you any information since most mental health and drug and alcohol treatment is confidential.
Let me know if you have any other questions I can help you with.
I hope this has helped you,