Hi Michael. Has your sister seen a physiotherapist to help with her headaches?? If not, she should see one, and they will treat her pain, and then start with rehabilitation which includes stretching and strengthening exercises, posture correction, correcting her work station - if it is her posture at work thats causing this, then its about lifestyle change.
The first step is to decrease her pain and then the rehab can start...it will make a world of difference.
I hope this helps.
Regards,
Reshma Namlal
Physiotherapist
South Africa