When a landlord caves to extortion or resorts to bribery they reinforce that behaviour and make it more difficult for me to do business.

The interpersonal advice--not legal advice--is to call her bluff.

Interpersonal problems are common.

My interpersonal skills, staying organized and having a process are some of my strengths. 

As a prospective investor, the interpersonal dealings are probably the most intimidating, and that's really part of any business, and yet everything seems exacerbated with the current economic and social challenges.  

As for the filth you would be wasting your time with any attempt to change their behaviour.

That's also one reason why they can present good buying opportunities, so I'd think about two aspects when planning your approach: 1) the deal itself; and 2) the inter-personal dynamics.  1) If the deal pencils, I'd dig into the intangibles to understand the risks and likelihood of closing. 

Even then, we did not arrive there lightly nor quickly; the gentleman was from an affluent family in a culture in which women are viewed as possessions and servants and we tried to work with him to move him from the views - or at lease the behaviour - of his upbringing.We had one other international student who up and left in the middle of the night (so to speak) leaving belongings behind and {appearing} to skip out on rent.  

I would suggest checking with other landlords in your area to get an idea of what they do but don't be afraid to set your own rules.Remember you are running a business and being tolerant of late payments only leads to more bad behaviour.

This is very typical behaviour of a professional tenant.