One problem for holidaymakers renting electric cars is that the charging infrastructure in rural areas isn't as thorough as it is on the UK's motorways.
Airbnb owner claims holiday makers running cables out the window is theft if electricity.
It seems like the obvious thing to do would be to get a metred EV charging point and bill the tenant separately. There are even grant schemes to help pay for the cost.
It's not like EVs are going away. Every house with a driveway is likely to have one eventually. She might as well get ahead of the curve.
Alternatively I remember when I was a kid my grandparents would spend several weeks in a holiday let that had a coin operated meter for the electric, we had to keep feeding it coins to keep getting power, surely they could do the same thing these days.