My little Fiona has a very sensitive tummy and she is also the kind of girl that inhales her food. I had her on Merrick and Vibrant Pets and her tummy troubles are pretty much gone. Vibrant Pets is something a lot of us here have our doggies on. Don't worry that you haven't been giving 'the right' food - it's all up to what your particular girl needs. I have one on Merrick, one on Wellness and my puppy is enjoying Orijen. You should see the ritual here at feeding time! 
Just make sure if you switch her onto something else you do it gradually, by mixing some into her current food over a couple of weeks, especially if she may have a sensitive tummy.
As for the chewing, like the vomiting it can also be a nervous/anxiety thing. Fiona chews sometimes if we are away longer than she'd like, it's always the corner of the same area rug.
I have three shelties and the one we rescued they had to figure out her age. Her vet (the same vet who does all the sheltie rescue dogs here) said she typically looks at the teeth first to get a guess on their age.
Give her time, Lucy took a few months to settle into her new home after living on the streets by herself.
Hope that helps
Just make sure if you switch her onto something else you do it gradually, by mixing some into her current food over a couple of weeks, especially if she may have a sensitive tummy.As for the chewing, like the vomiting it can also be a nervous/anxiety thing. Fiona chews sometimes if we are away longer than she'd like, it's always the corner of the same area rug.
I have three shelties and the one we rescued they had to figure out her age. Her vet (the same vet who does all the sheltie rescue dogs here) said she typically looks at the teeth first to get a guess on their age.
Give her time, Lucy took a few months to settle into her new home after living on the streets by herself.
Hope that helps
