If they're nervous opportunists, they might move out for a fee or even a threat.

If he owes her any money, they could threaten attachment of a civil judgment of $$ on him, and that threat might leave him to sign the agreement in lieu of having to owe her money. 

Most likely the tenant is annoyed at what appear to be dubious charges, and thinks threat of a law suit is necessary to get the landlord to pay attention. 

The rising sea levels are more of the threat in Miami Beach locations, from what I heard, but I'm sure it controllable.

Fortunately the threat of triple damages using a good local attorney allowed us to get this one.

It isn't a threat.

And are only just now starting to rise.BiggerPockets has an article about this (https://www.biggerpockets.com/renewsblog/2016/07/06/landlord-financial-threat/); most investors are more afraid of Physical vacancy than they are of Economic vacancy.

In my first 2 years of renting I have had 3 move outs. 2 were bf/gf breakups that ended end death threats ; abuse ; etc and these are on high end rentals.

Could be overkill, but the threat may make them open up.

You will be a triple threat (and then some) able to share knowledge on rentals and landlording, flips, and even the contractor and DIY forums...