Maybe the formality and intensity with which you treat this issue will force him to stop smoking it. 

This is a great case study for why partnerships should be formalized with an operating agreement.

It is best to do exactly what you have done; post the "formal" notice to vacate so that your tenant understands you really do mean business in terms that she needs to move out.

@Andrew SavageNot an expert in this topic as I was taught not to pull from "formal savings" to invest. 

@M Blue ah, so formally you won't be purchasing again....you already own it (or your LLC does)...but you can refinance it in your LLC if you want.  

There's no formal partnership or payment structure, just a kind of deal by deal agreement we discuss.

You may have purchased a house with a living room and a large formal dining room yet tenants don’t need both.

I have mailed a formal introduction letter letting them know how to pay rent moving forward and submit maintenance requests.

https://www.biggerpockets.com/..Personally I'd also suggest looking for a single family home that is essentially duplexed (even if not formally). 

However, in my experience with evictions, the tenants usually see that they need to get out once the "Pay or Quit" notice is posted - especially if the landlord has already documented everything to the tenant such that the POQ posting is a mere formality.