Even if you don’t have the money to buy a camera to record her, you can use an old phone or tablet. Download an app, point it at the door, and Bob’s your uncle you now have a surveillance camera. :)

My question is, what do you want to do about it? Sue her for emotional distress?

If you can afford it, why not install a home video surveillance system? Just one camera pointed at the entrance. Then, if she does it again, you can catch evidence. If you take her to court you need evidence. 

Are you moving? Is that why she brought people in? 

I agree with you, I hate renting for this reason, I hate having my privacy invaded like I'm their slave living in my slave cabin. It creeps me out. Other than installing a video system, I don't know what else can be done about it to catch them in the act.

Catching them is one thing - then you have to prosecute or take them to Small Claims Court. Then you have to persuade the judge this was reprehensible behavior that deserves $$ compensation. Then the landlord argues that it was an urgent situation to show the unit and she's oh so sorry and (she lies) and says she won't do it again. She makes a sad face and apologizes, and then you look like a B

I'm fairly certain my landlady faked an email to cover her tracks