ALL headaches types - an overactive brainstem. You need to understand whether or not the neck is playing a significant role in causing the overactivity in the brainstem or not. If it isn't you are wasting her time and money.
Thanks Blue Bear for your comments. As you mention it is not always so black and white and often the neck is merely a symptom of something more central in origin. That said the examination and treatment of that region often results in reduction of symptoms, if not only for them to return if the underlying cause is not addressed. An assessment by someone with an interest in the neck and its relationship to a headache is a worthwhile investment of time and money. After all it might be able to assist rule it out more thoroughly if it is not the primary problem.

I would not suggest she would be wasting her time if the neck was not the problem. The therapist should be ruling it in or out and if it is ruled out then they would move on to examination of other hypotheses and/or refer on to others for advice.