She uses no fertilizer or pesticides. She has thick, dark green, weed-free grass which requires frequent mowing. This is a good time to talk about soil quality too. There is a big difference between dirt and soil. Soil is rich in microbial life and has a lot of organic matter in it.
Dirt comes in many forms and it's a challenge to get anything to grow in it.
One part compost to two parts dirt is a good mix. But there are some weeds that are almost impossible to get rid of, no matter what. Some of these are even resistant to the chemical army. These two have HUGE root systems that might go as deep as thirty feet into the soil. They spread with rhizomes, just like your grass.