Im trying to go about this deal here in Lethbridge iv found a proper I want to purchase for sale by owner she hasn’t listed it yet but is willing to hear me out on a private deal without her being on title.

In instances of displacement like this you usually would have to pay her a fee for her being away from her home, hotel fees, and sometimes a meal stipend because she cannot cook for herself like her usual condition. 

Water and mold everywhere; they had to remove the vapor barrier and bring in drying fans.

Personally I did not have to open the drywall to show studs/insulation, but I did have to apply a vapor barrier to the slab.

You don't want to be responsible for her being in danger and you don't want the drama.

I still remember how it stank (no respirators with organic vapor cartridges to be had).

As far as her being afraid of the roommate, she will need a police report before you change the locks. 

In the back of my mind, I knew I could not keep good tenants in the place with her being the disturbance she was.

If you can follow the pipe into the basement or similar, you can verify if it's connected to a gas line.One thing to watch out for on "ventless" gas anything: if you use it a lot, you'll put a lot of water vapor / humidity into the house.  

The house has work needs to be done with support beams (rotted) and a lot of rotted siding spots where new wood, insulation and vapor seal need to go up.