I would start by telling him/her about her addiction so that s/he can refer her to an inpatient
rehab center. When she is done with
rehab, she can go to Narcotics Anon meetings, and see/do whatever else they recommend at the rehab center.
Now, there are doctors that specialize in addiction and pain management, but it really seems like she needs to get into rehab...fast.
Hopefully others with more experience will chime in.