I've been through this. The first thing I would suggest is that you make an appointment with her doctor to see what is going on. The doctor may refer your mom to a neurologist.
Others have mentioned using a plausible fib such as insurance requiring an annual physical for anyone over 80 or they will be cut off. You should probably give the doctor a heads up about what has been going on when you book the appointment.
I would imagine your mom might be petrified that she's "losing her mind" and is facing Alzheimers or dementia. You can assure her that there are many causes of auditory hallucinations that have nothing to do with dementia or mental illness. Some medications, stress, waking up from a deep sleep, being malnourished, being sleep-deprived, there are all kinds of causes. If you can reassure her that it could be something that is treatable like high blood pressure or getting the flu, maybe she'll consider going. Good luck and please keep us posted.
I've been through this. The first thing I would suggest is that you make an appointment with her doctor to see what is going on. The doctor may refer your mom to a neurologist.
Please keep us informed!