Renter Abuses AC, does anyone use landlord thermostats?

[Elle Bee]

I have a prima donna renter. Only drinks Evian, only drives new cars. Only….you get the idea. 
HVAC system tests out fine. Nothing wrong with IT, but she told the technician she needs to be “freezing inside during the summer so she can wear sweats and wrap up with blankets.”   

I’ve sent two different companies out to assess our unit. Tune ups, coils are cleaned, refrigerant fine, even replaced capacitors, topped off the attic insulation (just in case) AND had the duct work sealed. 
Nothing wrong. I made sure she was present at both appointments, and she told the owner of the company that he can say it’s fine if he wants to but she’s “not going to be happy until she gets a new system.”

Extremely cool summer so far and she’s already started with text messages, which I respond to by email. 

At the same time, she has failed to send pictures of the hvac filters getting changed out every month as the lease requires. And her rent never arrives on the day it’s due. 
She’s exhausting. 

Her lease is flexible from 1-2 years. 

Since the lease is a 1 year with a possible extension to 2 years, (they did not know when they moved in how long they’d need the unit so the first year is solid, the second year is an option.) 

Do I have to give a reason for ending the lease at the 1 year mark?  

My hvac technician suggested he install a landlord thermostat to keep her from running our current unit into the ground. 
does anyone else use these? The limits on AC is 72  and the furnace is 76.