@fairymystry, you are a good friend to help find answers for your friend. I know you are very worried about her and want her to get the help she deserves. It sounds like there are more questions that need to be asked until you and your friend can get an understanding of what to do next.

Mayo Clinic does not require patients to be off of opioids or other pain medications before they can be seen. That said there may be situations or programs for which this is a requirement, such as the Pain Rehabilitation Center https://www.mayoclinic.org/departments-centers/pain-rehabilitation-center/sections/overview/ovc-20481691

As a best next step, I recommend that your friend confirm with her referring physician that they contacted Mayo Clinic. Find out what the requirements of admission are. Since your friend was intially accepted, her doctor can work with her to meet the requirements of admission. If admission depends on adjusting her current pain managment plan, her doctor can work with her and Mayo Clinic to meet the requirements and manager her pain.