Normally I'd recommend against litigation or anything that involves our legal processes, but you've a simple case from the sound of it. 

What is the effort involved in this type of litigation?

I'm a litigator so I did it myself.  

Also scrub against Previous Litigant Scrub-- here's great vendor http://www.donotcallprotection.com

My lease to the tenant contains the below term:“TENANT PROTECTION ACT OF 2019: This property is not subject to the rent limits imposed by Section 1947.12 of the Civil Code and is not subject to the just cause requirements of Section 1946.2 of the Civil Code.

You should be able to have a civil discussion, back and forth, citing guidelines, without anyone's ego getting in the way (hers/his OR yours), or you should fire her/him and pick a new originator - ideally one that knows their investor guidelines well so you don't HAVE to do the back-and-forth.

There is no point in involving the police so they are unlikely to do anything, given that this is a civil matter, not a criminal one.

I've been able to see these conversations as a Civil for the developer working with the dry utility consultant regularly.

I did not see any entities named Vaughn Investments & Property Management or any fictitious name filings / "doing business as" Vaughn Investments & Property Management.I would, however, suggest that for any person or business that you are considering doing business with in Missouri that you search their personal name and the name of their business on the state courts' electronic records website: https://www.courts.mo.gov/casenet and clicking "litigant name search." 

My career profession is in Civil Engineering.