The more you change up the food the more the dog will refuse to eat. She's learned that if she stops eating one food you may give her something "better/different". Eventually you'll be left with a dog that'll refuse most foods.
Kali tried this with me. I simply kept feeding her the normal foods and after she was no longer a tiny pup took whatever she did not eat in twenty minutes. Then, another serving after the human dinner with the same taking back in twenty minutes. Yes, she went hungry a few times.. but she'll eat anything I put down now!
Dogs are too smart to starve themselves and I wanted to feed her the best stuff possible and not the dog version of 'candy'. And please note.. she never even lost her bit of dog squish.
How big is she? That'll tell you the total amount per day. My girl is 4.5/5 pounds and gets a third of a cup raw for breakfast and about a fourth of a cup at night. I was feeding her a second third of a cup at night but she never finished it.