I agree with @Jimmy Woodard on the mattresses and linens.

It's furnished, but I'm a couple hours away so I don't want to get into regular cleaning, linens, etc. like an STR would require.

You usually have to add furniture, linens, cookware, artwork and such.

I am hoping there is some clever way to keep the Roku stick & device from disappearing to begin with.

Unfortunately, she's extremely manipulative and clever.

Pretty clever, actually.

As to wifi thermostats - if you provide the wifi, I guess that might be a worthwhile option, but if you don't ...Even with you controlling the thermostat, tenants have cleverly identified methods to "defeat" landlord controls, such as ice packs placed in proximity to the thermostat, or just opening windows in the room where the thermostat is located. 

Threw a butcher block countertop above them and installed wall cabinets above that in place of the missing linen closet.

These people are typically schemers, who think they have developed a new way around existing laws - as if they're clever.  

Buy all linens new, but inexpensively.