Hernia

My cat had a hernia surgery last week. The hernia was spotted by my groomer the week before. The vet is stating that the hernia is due to a spay she had done 3 years ago (spay completed by a different vet). She would've been groomed about 2 months prior to the recent grooming session and would've been checked over previously by the vet on a number of occasions without noticing a lump on her stomach. My question is: Is it abnormal/unusual for a hernia to appear 3 years after a spay surgery?

Hello - yes, it is rather.   If the spey was three years ago, I would have expected the sutures to have dissolved long ago and the wound to have been holding by itself.  Might there have been extra pressure in the abdomen for some reason?  A healing abnormality?  Your vets may want to find out more about this, depending on the context.  Furthermore, worth double checking (unless you remember) where the scar was, as many cats are speyed in the flank now.  Was there a hernia orginally, perhaps?  Might she have been pregnant at the time?