Greens and in this case, grasses, are an excellent source of vitamins and minerals; so it may be that your cat is just "supplementing" her diet with a needed vitamin or mineral.
I think that most animals, like dogs and cats , will eat grass from time to time. Even parakeets like to have some greens; so it is not just when something is wrong, or the animal is sick that they eat grass.
Many people actually grow greens for their pets to eat.
You may have heard of wheatgrass ? It is highly nutritious, and is very easy to grow. I just use an old baking pan, or even one of those cheap ones from the grocery store, add a little potting soil, and mix in some wheat berries.
Once they sprout, they will be tender and tasty to your cat, plus you won't have to worry about her picking up anything bad from the grass outside on your lawn.
As the wheatgrass grows, if your cat is not eating it all, trim it back a little so it makes more tender sprouts.
Your cat will love you for the delicious greens, and be healthier for eating them.
