Just a suggestion since we had a male with the same symptoms.  We found that
he had a urinary tract infection which he was misinterpreting as a sexual
urge.  Of course, this could also be an incomplete neuter (one testicle not
removed), but you might try your vet's choice of anitibiotics first, before
thinking about surgery.  I am not a vet.  I am a vet tech, running a ferret
shelter.
                     Regards,
                  Carolyn Kinsey
           Ferret Rescue of the Western States
[Posted in FML issue 1419]