Thinking about doing eco-friendly things again, but...

I've talked to one of my friends about how often she drives a car. Everytime she goes somewhere, she drives. Even when she goes to 7-eleven which is about only several minutes away from her house. Also, she keep the engine running while she goes into the store. I told her that maybe she should walk instead of driving because driving everywhere even such a small distance only sounds wasting of gas, unhealthy and is not eco-friendly. However, she said that she always thought about it and she knows it would be better if she did so. But still driving a car is easy and convenient for her to do. She also said that she might sounds just being lazy but the environment won't change even if she walks instead of drving a car. When I heard this, I thought it sounds kind of familiar. I believe that such small thing does little but still necessary. I also thought that maybe there are more people tend to do same thing as she does although people tend to say, "walking is better than driving a car for the environment" when they talk about the eco-friendly things, but It seems difficult to keep doing those things in everyday life....? It still makes me a little confused.