Why is my dog throwing up 5 hours after eating?

I got a boxer / collie from the vet on Saturday. They said she was vomiting at night but, they say that because they thought she was eating her droppings. Well since I got home I tried 3 different foods and out of 1 cup she would only eat an 1/8th of it. She is really skinning and can see her rib cage. The only way to make her eat more is add some kind of wet food but, 4 to 5 hours later she tosses it up. The vet in town gave me a food he thought would for sure work and she still does it. Also if she is eating it to fast wouldn't she throw it up right away? One last qwestion I got this dog from humane society for 200 dollars do you guys think they should of even let her go while this was happening and if i try to return her should I get my money back. I really dont want to do this but, we got 2 kids in the house one 3 and another 4 months and we need to get her house broken and use to thew kids before a Minnesota winter.I had a cup a food in there all day from 4 this morning to 5 tonight and all she eaight was about an 1/8th of that cup. I put some in my hand and act like it is a treat and she just turns her head the other way. but when I put some wet food in it she goes right for it like she is starving.

If a dog eats the food too quickly it will throw it up immediately. For dogs with sensitive stomachs, serve the food in tiny portions, wait for them to relax a bit, then feed more. Mixing different foods the dog is not used to also messes up their stomach. New brands of food should be introduced slowly. You can't return a dog to the humane society and give your money back. Most of the time, they'll charge you for bringing a dog to the humane society.

I have a dog with ibs/colitis problems, he has a very sensitive stomach. He throws up if he doesn't eat on time, if i don't feed him right away he throws up. You could go to the vet and get canned medicated food, this worked very well for my dog when he was having issues. It wasn't very expensive, but it was essentially chicken and rice. so if you wanted you can cook your own at home, just some grilled chicken and rice mixed together, its a very bland diet that helps. You can start introducing dog food in to the chicken and rice after a few days or so.