I assume she knows everything in the area is not sprayed with any type of *acide.
https://www.livescience.com/32435-why-cant-humans-eat-grass.html
Lignin can be hard to break down by human stomachs. Not only that, but the lignin in food can actively inhibit the access nutritional benefits of other types of digestible fiber
Your dentist would not be pleased; grass contains a lot of silica, an abrasive which quickly wears down teeth. Grazing animals have teeth that are adapted to continually grow, replacing the worn tooth surfaces quickly
There’s usually just a handful of dangerously poisonous plants in any given area. If you learn those then most other stuff should be safe-ish.
Except for all the parasite eggs she’s eating
Not really a thing in my area, excepting aquatic plants. Can’t speak to the whole world.
Unless by your area you mean a place that doesn’t have plants in the first place because it’s entirely paved over, I promise you that there are animals that will shit parasite eggs onto the grass, and children are particularly vulnerable because they both do dumb things like eat grass and have weaker immune systems.
Pinworms, for example, are basically everywhere, even if most parasites are tropical. They’re so pervasive they’re even noted for not following typical affluence infection rates.
First, pinworms only cause mild illness. My point was your child won’t die from eating random plants with a few exceptions that are easy to learn.
Second, pinworms are not spread by animals, only human to human. I don’t think eating plants is likely to be a vector.