I have not read through all of the replies so I'm sure that something similar to what I am about to post has already been posted but, here goes...
My Stedman was always a REALLY picky eater - not only with his dog food, but even with his treats. He had gotten soo skinny at one point that it literally looked like I was starving him. Obviously I wasn't, it's just that HE didn't want to eat. When I would give him a bath and he was soaking wet, you could just SEE how skinny he was - his little ribs and even his spine. I mean he didn't look MALNOURISHED like some of these dogs do that you see on all the animal cop shows on Animal Planet, but he was *extremely* skinny none the less - way TOO skinny. And I knew he was hungry because I could hear his stomach growling soo loudly all the time - and he would throw up the yellow bubbly bile because he was just so darn hungry.
Like you, I tried a gazillion different foods and like your baby, my Stedman would eat the new food and love it for the first few days, and then he would show absolutely NO interest in it what so ever and he would just flat out stop eating all together.
I used to feed twice a day, and then I decided that because he was like this, that I had to start free feeding again and just leave the food out all day long - literally, day and night - never taking it up. Since I have started this he now eats whenever he is hungry. He still isn't a big eater, but he DOES eat and he doesn't look nearly as skinny as he used to. He is still a very tiny guy, but not so skinny to where I can actually see a bunch of bones sticking out anymore.
My advice is this - find a food that she seems to really love and eat the MOST at one time. Once you find that food, STICK WITH IT. *Do not* give her a new/different food 3 or 4 days after she stops eating the other food. You have to let her know that her pickiness is not going to get her whatever she wants. Once you find a food that she seems to enjoy, stay with that exact food and leave it down where it is accessible to her 24/7 and do not take it up. Once she knows that this is ALL she will be given, she will learn that she has to eat it when shes hungry because nothing else is going to be given to her. Trust me, after a while, she will catch on and get the hang of it and she WILL eat when her little tummy tells her that enough is enough of being hungry. It worked like a charm with my Stedman and he was the pickiest dog I had ever seen in my entire life. He would even turn down HUMAN FOOD - now what the heck kind of dog actually turns down HUMAN FOOD when you offer it to them? Not many.
Good luck with your baby girl. And by the way, I feed Natural Balance Potato & Duck Small Bites (it is Grain Free and is great for allergies as well, which my Tatum has) - and my Stedman really seems to love this food. He was a little picky with it at first, but now he eats it really well
