All adults, unless legally incapacitated or something extreme like that, should be treated the exact same way in your application process.

The other tenant has a 4+2 for $900 a month and three adults...

As  an adult the parents only have limited influence unless they are her legal guardian.   

We rented our house 4 years ago and now the tenants abandoned and left with their adult kids living in the house.

@Christopher ChristianI can not speak on formal education, have been self employed for most of my adult life.

In California, an accepted occupancy limit is 2 occupants per bedroom + 1 (where an occupant includes adults, seniors and children).

Mother-of-Two’s older daughter, Daughter Occupant (who was by then an adult), requested to continue occupying Owner Gone’s home, by herself.

Of those who show up, I email the $35/adult the applications.  

None.All adults over age 18 must fill out application and submit to background check. 

If the author had help, no doubt there were probably countless arguments over the design of the algorithm "hey you've got this all wrong where you count the number of "adult bookstores" per capita as a positive, cities with lots of them are dumps!"