Hello Nancy,
It seems to me you have another property management issue. This is a prime example of why I have not moved to PM's with my rentals yet. Personally I would fire your PM and continue to manager yourself, do you have the ability to hire an assistant to help you with the screening process? I find that is the most time consuming part of managing my properties. Maybe you don't need a manager but an assistant or agent to source out your tenant screening to.
As for the unauthorized tenant, the tone has already been set. If you don't at the very least get the unapproved tenants out they will think they are in control. I have already seen this in my business by relaxing late fees. Every time I bend on my rules from that moment forward you can bet they will be late again the next month and expect the same thing. I had to learn the hard way YOU must set the tone early and keep them honest especially in the first lease. I alway find a reason to be at the property at least once a month for the first three months of a new tenants lease until i'm comfortable with them and get a feel for what kind of tenants they will be. This way you don't have to depend on the neighbors to tell you there are too many people in the house.
Hope I could help,
Matt