Have you tested for hyperthyroid? Hyperthyroidism Symptoms in Dogs | eHow.com
I know its more vet costs, but if she matches any of the symptoms listed on that website, it may be worth looking into...
As far as the food you fed... Even though it is "name brand" puppy foods, doesn't necessarily mean it is a good food. I'm not a fan of Science Diet.. Its got a lot of fillers and is chemically altered to make your dog like it. Its also not that high in fats.
The dog food I have had the best luck with weight gain is Pro Plan adult high preformance. It is for working dogs and is full of calories and fats. My mo runs a rescue, and our skinny, starved dogs get that food for weight gain.
Another food I like is called EVO... It is an alternative to the RAW diet and is full of calories as well. It is expensive, but it will put weight on your dog. Blue Buffalo carries a food similar to the EVO brand... not sure if its cheaper.
There are supplements you can feed.. Its not table scraps.. but an actual reciepe for skinny, starving dogs. It was designed for rescue dogs that are losing weight due to stress... and stressed dogs have a really hard time keeping weight on. Holistic Dog - Satinballs Satin Balls
For now, you would feed this with the high protein and high calorie diet.
I realize your frustration and feeling of going broke... but try the satin balls and maybe sample some of the higher quality foods. Table scraps only put fat on a dog. Dogs cannot use fat the way we can. They need protein. Eggs are good for coats, but they're not going to put weight on your dog... Any type of veggie is a fiber source and will just make your dog poop more. Follow a recipe that is designed to put weight on dogs that are having problems putting weight on.
I hope I helped.