Sounds like static to me, may even be effected by the fabric conditioner she uses. Is she stood on a water proof / rubber floor? Sound like she is not earthed but the desk is. You could sugegst to avoid wool clothing or change foot ware?

Just a thought, I like interesting problems like this one :D

Let us know if/when you find a solution

Des

Whats the type of flooring and also the type of castors or wheels on the chair she uses.
What type of clothing does she wear as per above as wool and other synthetics are often a prime conductor.

Static charges are also more likely to build up in times of low humidity, as experienced during the recent icy weather. Barrie's solution of plants is a great one to increase humidity.

Hi, best solution is not to ground the chair, but to ground the desk. This will prevent the build up.
I had a similar problem with some shelving and tried insulating it, siting it on rubber mats etc... no joy!
Eventually attached a copper wire to the frame and drilled into the floor to ground.
I think its important to attach the grounding wire both to the desk and the floor to ensure a sound connection.

Hope this helps!

I would be very careful connecting the desk to a true earth such as a rod in the ground if that is what you mean.
Static dissipation devices, offer a high resistance path to earth, sufficient to leak the build up of static charge away, but, not sufficiently low to import a potential that would not otherwise exist in a location.
If your desk is built to the "office furniture electrical standard" the number escapes me at the moment, then it should be connected to the earthing of the building.
Is this your issue?
Also, if the desk is not earthed via the building system and you earth this through a rod, your building earthing system could well be connected at the origin to a TN-C-S (PME) system.
You could now have earths within a single location which are reachable that could be at different potentials, sufficient to cause electrocution in the event of a fault.

Simply connecting metallic objects to earth when a fixed electrical installation is present in the building is not a good idea!

As SimonL suggests above, are there any real shock issues, I doubt it as there have been no serious reports and I would guess that the sensation that is being felt is a sharp needle like "crack" which is probably static discharge.
If there were real issues from the fixed install I would expect a description of tingling.

You may find that it is the person who is carrying the charge, there is a test, quite safe, IF your electrical installation is SAFE.
Get the "sufferer" when they expect to be charged, to touch the metallic body of an electrical accessory, such as a light switch, or socket outlet, and see if they get the shock then.
The metal box will be connected to the building earth "network" in the fixed installation by a very low impedance connection.
If they get the "shock" then they are the charge carrier.
This should pose no health risk to the "patient" as they are already experiencing such shocks.
The micro amps of current from their stored charge will pose no danger to the electrical installation either!