if they are classed as a wild animal, and quote " a danger to the public " then they have to be licensed, ! if they do not have to be licensed then they are no danger, and not wild they are domestic, if they can be handled then they are tame by definition, sounds to me as if this woman has something against ferrets, i would go over her head go straight to her superior, and make a big song and dance about it, chances are she will back down, play a predujice card, i fecking hate jobsworths.
give her loads of stick, i would get the rspca involved, local papers etc. ( if you got permission then thats the end of it )
make her realise that she aint that important.