She may not be purebred, if she is you may want to try different foods, my pup wouldn't eat so i changed to kirkland, much cheaper and better, $35 for a 40 pound bag, for the natures domain stuff ( salmon, sweet potato , rice ), my cousin's dog tried the kirkland puppy food, but started getting real sick, so that's not something i recommend. Did you see the parents? Get her checked out she's too small. And like someone said she may be younger than 8 weeks, if a mastiff. In that case that could be the reason she's not eating dry food, try to feed her mush. With dog's what you do is not a learning experience, you gotta do it right the first time, she may have worms, my puppy had worms, and was throwing them up at 8 weeks. A deworm should be near, there's a huge chance and i hope i am wrong about the worms but you should start mixing some water in her food, keep her hydrated. Just my two cents.