At one point she buried her face in her hands and I couldn't help but think about her being in the home by herself with so many years of memories.

All new windows (some larger, some removed), new floors and paint, removing a few walls that aren't structural, two net baths, making a basement into a room, closing off another room by extending the floor a little and adding a very small piece of wall, adding a swamp cooler, new water heater, vapor barrier, replacing kitchen cabinets, adding tub in one of the bathrooms, moving toilet bowls a little, adding a larger deck, etc etc

If she isn't a criminal & as long as you feel comfortable with her being there I don't see where the problem arises.

Any requested fee not payable on closing day would obviously vaporize the loan in my eyes.

You may be right on her being nervous as this is her first apartment and I don't want to scare her, just want to make sure she knows who to call if there's an emergency and who/where to pay her rent.

This creates a vapor barrier that prevents humidity and odor from entering the interior of the house.  

Cons: more maintenance, higher utility bills, need preventative maintenance in place (vapor barrier, adequately sized dehumidifier, HVAC/mini-split), higher insurance. 

She rents her bed room.

I hope the insulation doesn't have a paper backing (vapor barrier) on one side otherwise this will cause a condensation problem. 

A couple years back, California redefined "Tobacco Products" to include vaporizers regardless of whether someone is vaping Tobacco, tasty flavors, or marijuana.