I state upfront that a key lock box, or garage code that gets me into their home is fine (though if there is no power to the garage door - (power outage, problems with the pad itself) you can’t get in the house.
You can explain that - for you and your safety, bending over and fishing out a key from underneath a mat or plant puts you at risk for an assault/unwelcome attention and such things. Further, standing upright allows you better situational awareness around her residence - for unauthorized people trying to get into the house, squirrels, bunnies and other delightful chase-able varmints - loose dogs kids on skateboards - all that strange stuff that goes on.
The key lock box offers the owner and you piece of mind, as only the person who has the code to the lock box can get into the house, and they can change it any time. When someone’s residence is broken into, one of the first things the police and insurance company will want to know is how the house is secured. Oh I leave my key under the mat, and the homeowners/renters insurance may not pay.
The key in a lock box or the garage code - is the best way to protect you and the dog owner.
There are many different kinds of lock boxes and amazon has the best selection. The stores in my area don’t have the best selection - which is unfortunate as I would be happy to refer them