Even though carpets are professionally steam cleaned between tenants it is not unusual for someone who does not have a pet to walk in and comment about a pet odor (and this does not have to be from animal "accidents"; but simply from a pet living in the area.)Ironically I do animal rescue myself (cats and dogs) so no carpet in my house! 

Does she have pets - any pet odors (owners don't realize that pets have an odor).Have someone give the home a good look and give her an honest opinion about anything negative about the house.

SANITIZING AND ODOR REMOVAL (IF ANY) ARE NOT INCLUDED HERE AND WILL BE PART OF THE RESTORATION PROCESS.5.

I can see some owner make tenants to allow showing, where for some who don't care, you'll have to step over their mess, and I have to apologize, or hear them grumble they have to straighten out the place every day, and make sure the stuff is not stolen.

Ozone generators work magic for certain odors, but not for all.The ozone machine doesn't make people sick like the flu or COVID.

Noise and odors etc... for your residential tenants. 

Is there an odor in the building?

Depending on how rank it is and how big the place is, anywhere from half a day to a week will eliminate the odors.

I use zep smoke odor eliminator. it works well for spoke and cooking smell.Spray the whole house includes vent. the next day the smoke is gone.

I also give them common examples of deductions that may occur due to ripping out floors for pet urine; trim/door damage; pet odors etc..