It sounds like the dog had vestibular disease. Often dogs that have had this condition have a head tilt which continues after the problem is resolved. Sometimes the head tilt will last a short while and sometimes it is permanant. Often vestibular disease is caused by eari infections or even old age or not cause determined (idiopathic). The continued head tilt should not affect her working ability. You can read about vestibular disease here:
I hope this information is helpful to you.