I'm not sure that the food supplements are healthy. Rinsing the area with water is the best solution or training her to go somewhere else in the yard without grass. My dogs actually prefer the gravel path. You can also build a sandbox.
I looked up this problem once and it's caused by nitrogen in the urine, which is from the breakdown of protein during digestion. You can reduce the nitrogen content by reducing the protein content in the food. But I don't know if that's a good idea either. There are those who say that only active working dogs need high protein food, but I tend to disagree with that.
By the way, it's a myth that only girl dogs cause spots on the lawn. It's just that girl dogs pee in on spot, concentrating the nitrogen content, whereas boy dogs pee in a stream spreading it out and less likely to make a spot.
Generally I find that my dogs don't have enough pee by themselves to make a spot, but when one goes, the other has to pee on the same spot, then any guest dogs pee on it too. And I get spots.
That's about all my knowledge of Yorkie pee
