You do not give a lot of information on your assessment or treatment, which makes it impossible to get to the bottom of this problem.
Can you answer these questions please:
-Is Cervical spine movement impaired (or hypermobile)? Which level? Are the CM joint movements impaired?
-Are triggerpoints found in muscles around the cervical spine/ CM joint? for shure the ones which have their neuro origin from C0-C4.
-Has she had tinnitus longer than head aches and neckpain?
-Has she generalised pain, Yellow flags?
-Condition of teeth?
When you are able to answer these questions you will be on the way to find the answer.