Back in the days when cars had the little button on the door one would push down to lock the door.
You lock both doors. When you get to the car with your girl, you unlock her door, help her in then walk around the car to unlock your door.
If she reaches over to unlock the door for you, she’s a keeper. If she doesn’t reach over the seat to unlock your door for you then get rid of her because she is selfish. :-)