Jimbo
If you go the appointment with her (i.e. leave the car) then I would expect your use of your Badge to be perfectly valid even though it is not your appointment, however, if you stay in the car then the recommendation, in the pamphlet that accompanies the Badge, is that once you have dropped her off that you park in a non-disabled bay, I don't think that her having a badge would alter this.
What I will say is that I have no idea how likely it is a that a traffic warden or similar would challenge you on this if you were displaying your Badge in the car.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
