Was thinking of some sort of electronic door lock on the front door. Anyone use one? How secure are they and which type would be the best to look at?
But you are always home so why bother?
As others have said you need to introduce the independence and the responsibility that goes with it.
The reason for their popularity in offices are:
1. When someone leaves you don’t need to worry about getting keys back (you presumably aren’t worried about that!)
2. When someone loses their keys you don’t need to worry about whether they had stored them with anything that identified the address (you can get round this by training her not to put her address on her key ring or store keys with ID just like you do, right?)
3. You don’t need to be concerned about unauthorised copies of keys. (I assume you trust her not to copy the key and give it to a dodgy guy down the pub?)
4. You can have one electronic key that unlocks multiple doors, and which is configurable to work differently at different times, zones etc. (I assume your house is not so large, or your rooms so secretive to need such zoning!).
These systems often fail open when the power is off. That is a sensible solution as with a power cut you need to be able to move around and in the event of a fire you need to get out. In a home situation that doesn’t work as you would want to be secure in a powercut when you are not in. You can get lock on failure systems too, but you really need some sort of mechanical over ride (e.g. a key) for them or a fault in the electrics will mean you are locked out permanently, and powercut leaves you outside. So you end up carrying a key anyway!