Has she had any bones, rawhides or other non food items lately?
Any change in stools?
Is the area tender if you touch it or hot?
Any of the following symptoms?
I am very concerned, your dog is experiencing symptoms of bloat or a blockage from the rawhide. Rawhides are never a good treat for the dog as they can cause a blockage in the digestive track which is very painful for your dog.
Bloat is a stomach condition of dogs that is potentially fatal. Bloat refers to the stomach becoming very dilated with food, water and air. The most serious form of bloat occurs when the stomach also twists on its long axis after it is dilated. This is an emergency situation for the dog. If not treated early on, especially when the stomach twists, the dog can die in a matter of hours.
If your dog shows signs typical of bloat, you should seek emergency veterinary assistance the swelling on the left side is one of the most common early symptoms of bloat. As mentioned previously, waiting until the morning may be too long. A blockage is also very dangerous as well so to be on the safe side I would recommend having him see by a emergency vet today.