I'm thinking of using that tactic against the non-responsive owners of the run-down MFR's/SFR rentals in my area, even if it feels kinda like I'm "playing dirty."  

It's a sneaky tactic used by so many these days.  

It's important to look at a nationwide report because they might have been convicted of an offense or be on a sex offender list in another county or state and you deserve to know that before renting to them.Another powerful screening tactic is to get an address history report so you can compare their actual residential history with what they claim on their application.  

Or other helpful tactics? 

I wonder if you can sue her in a separate action for costing you money with fraudulent delay tactics.  

Sounds like more stall tactics to me!  

. :-)I don't like scare tactics that send people running to lawyers, when it's not necessary. 

Bringing three people into your home that are already friends will make it very difficult to get rid of the one that does not work out.You will be overpowered and bullied by the group and they will ultimately take control of the environment.

I will follow up if anything unfolds or if it's just a scare tactic.

I would never offer to extend the lease for even 10 minutes as a tactic for tenant requested upgrades.