How much does she weigh? Overfeeding can cause loose stools. Also, when you add water to the kibble, don't leave it down too long. It will spoil quickly which can cause problems.
1/3 cup wet food plus kibble (how much?) sounds like a lot.
Is the wet food a complete and balanced diet? Many canned foods are not and meant to be a small supplement to kibble.
Why did the breeder have her on "large breed" puppy food. That is strange.
As for not eating much, I had to hand feed Max his entire first year. We played games and he did tricks for me. Now he is a chow hound.
You might try game puzzles or a Kong, or training exercises to encourage her to eat her kibble.