Unstable tenant harassment and slander

[Jessica Young]

Is there any course of action for a tenant who repeatedly texts purposefully disrespectful things about how much they hate the rental and constantly tells you how much they regret renting it? 

It's gotten to the point that my tenant is now accusing me of misleading her, saying I "took advantage of" her and am overcharging for rent. She had 2 walkthroughs and the lease discloses no upgrades will be made/as-is condition. 

I used the happy clause 3 times and she CHOOSES to stay. But the texts go on and on.   

Even small repair requests are a nightmare drama she draws out forever.  She seems extremely mentally unstable. 

I've also come to find out that she slandered me to at least one handyman, to multiple neighbors, and to a friend who is her acquaintance. This is an out of state condo that I plan to live in within a couple years, so I feel like she's out there laying a foundation I'll have to work against to prove I'm not some rotten slum overlord, which I assure you I am not. 

If she feels she made a mistake, which she keeps telling me, do I have to just tolerate the constant complaining about it? She's only been in there 2 months and it feels like 20. 4 more to go. 

Is it out of line to ask the other person on the lease, with who I have no contact, if her mental state is ok? I'm not being funny. I'm worried.