Diagnosis may be accomplished using nothing more than a balsa-wood antenna painted silver to resemble a real one. Point it at the subject to see if she sues...
From the "However!" department: Some of these seemingly crazy psychosomatic reactions can have a real cause. I recall the long ago case of a (Swedish?) auto plant where CRT's said to have caused illnesses due to EMF were actually making workers in one office (but not another) ill, which turned out to be due to paint flecks getting into the HVAC ducting from the plant's painting operation nearby; attracted by the static charge on CRT screen, paint flecks were then being being repelled into the faces of CRT terminal operators, causing rashes, and eye and respiratory problems.
A similar effect may explain problems said to be caused by HT power lines; chemical reactions between air pollutants can be be facilitated in the electric field near cables and across insulators, higher voltages having a stronger field, with the reaction products being inhaled by those living close-by.
It is apparently too expensive for actual operating concerns to confirm electrosensitivity by running silver-painted rope instead of metal cables. Perhaps someone will apply for a grant.