I would tell her that, as long as she isn't short on rent or caused any major/medium damage since I bought the house and removed all of her belongings (emphasis on removing all of her belongings), I will return her $300 SD within a couple days of her move out.I would be thrilled to give a hoarder 300 bucks to get all their stuff out of a property. 

If your area is in a hot market and ARV is correct then there is something else causing the low ball offers.  

Low interest rates and people not wanting to sell and move during a pandemic is causing a lot of demand and not a low of inventory. 

But if the contract is non-assignable and the buyer wants to cause trouble then technically they could throw a monkey wrench if they wanted to. 

Some have suggested the pandemic has caused the low inventory in housing, but with interest rates so low and houses selling above asking, why would any homeowner not want to sell during this time?

Technically they are in violation of their lease since they didn't let you know within 24 hours, but do you have evidence the leak was caused by tenant negligence?

It basically let's her know that she is in violation of her lease (causing damage to the property, creating a fire hazard, inappropriate use of common area) and that she either quits/cures or will be evicted. 

I agree with all except the last set which would cause damage...and likely a call to the police.

Don’t go with a contractor you “feel” comfortable with and really like their personality, cause they can end up being the friendly guy who steals your money.

I know ethically, it's not right you get stuck with the bill, but I'm more concerned that you don't attach your name to something that could potentially cause you way more drama down the road.