Elavil (amitriptyline, a tricyclic antidepressant) is usually prescribed at a very low dose, 10 mgs or so. It is usually well tolerated. I have not heard of people having serious withdrawal problems with this low dose. An SSRI would be more problematic. You can often get good information about a drug from your pharmacist.

Has she had any treatment for her upper neck ? This is often a cause of head aches. It may help to ice her upper neck. A day of on and off icing would be worth a try. It is reduces her head aches, it points to neck inflammation. If she has any tenderness at the bony part behind her ears, this is indicative of an upper neck injury. They can be very subtle and still cause head aches. These head aches are sometimes responsive to Botox injections.