I also agree. The first thing to do is to visit your vet for blood work and to check the thyroid. Unfortunately, right now many breeders are ignoring thyroid issues in their lines thinking, "It's only a pill a day to fix it." We are seeing more and more dogs with thyroid issues, and thus weight issues.
If all is good, then the issue is simple. She is getting too much to eat. In the US, we often think we are feeding a small amount of food when that "small amount" is really a ton. Our view of food is very skewed. You say your dog "only gets fed at breakfast and dinner." I would omit the word "only" and feel it suggests a mindset here. Your dog SHOULD be fed twice a day - and that isn't "only." :)
I have a sheltie who gets over 1/16th a cup of food twice a day. He is in excellent shape and competes in agility. He obviously then gets tons of exercise, and I even do extra work outs for him since he competes in an athletic event. Yet, he gets a very small amount of food.
I suspect the real issue here is that your idea of a "small" amount is flat too much. If the blood work is good, then the dog is getting too many calories somewhere.
Make sure your dog is on a healthy diet. If you feed kibble, make sure it is a premium kibble. Also look into the low fat kibbles available. Discuss these options with your vet. I'd completely cut out the table scraps. My dogs don't get anything off of my table. That's my food - not theirs.
I teach agility and often have to tell my students their dogs are overweight. And BIG kudos to you for knowing this weight is so very bad for your dog's structure. :D My students always say, "But he hardly gets ANYTHING to eat." Then, as we start discussing, I find out how much "anything" is. Usually, the dog is getting a TON of food based on it's size. As I tell my students, dogs can't get in the car, drive to McDonalds and get a Big Mac and extra large fries. The calories are coming from some where!! I had one student who insisted she didn't overfeed. Upon talking with her, I had to agree. The vet report came back good too. She finally discovered her mother, who lived down the road from her, was driving home from eating breakfast out everyday and was throwing hundreds of calories in leftover breakfast over the fence for her dog to eat!! When this stopped, the weight came off.
Also, I find back yard dogs do not get the exercise their owners think usually. Add in some purposeful exercise too. :)