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Thank you all for your answers. We'll be seeing the doc again this morning, mainly to talk about taking her off the medication. I will be there and will ask about your suggestions.
Sqad, yes we know that stress is still a possibility, and she does use the stress and pain management techniques she has been taught, but they don't seem to make a noticeable difference. Unfortunately she has reached the point where she feels that she is "the headache" and no longer herself, which won't help.
237SJ, she has been seeing an osteopath (a cranial one at that) and after visits to him she does seem to improve a bit, but it's temporary :-(