Noise phobias are common, but you can combat those as well. Let me give you some preprinted instructions for noise phobias that I have written up. After that I'll talk about her appetite and mouth behavior.
Noise phobias and anxiety is really a common problem. Many dogs have reactions to different noises. This is really a problem around the 4th of July and fireworks. For things like thunderstorms, some people tape the noise and play it back at lower volumes while playing with the dog and providing positive reinforcement for the dog's lack of anxiety while the noise is played at low volumes. Positive reinforcement would include calm praise and hot dog slices or other tasty treat (not regular treats. You then gradually increase the volume slowly until your dog is desensitized to the noise. Your vet could prescribe a medication called Acepromazine, which is a tranquilizer. You can read about this here:
Another prescription drug would be Xanax but I have to caution you not to give any prescription drug to your dog without consulting your vet first.
Many people get Rescue Remedy to help with noise phobias. Be sure you get the kind that does NOT contain Xylitol. You can read about this here:
It may also be available in your local pet store as well. Benadryl is often used as it does tend to calm your dog. Benadryl can be given to your dog, the dose is up to 2mg per pound every 8 hours. Benadryl in not a sedative though so it won't put your dog to sleep. Leaving a TV playing loud also helps prevent your dog from hearing the outside noises. Another treatment is Melatonin which you can read about here. It has been shown to work well for noise phobias.
DAP collars might help a bit as well. They produce pheromones that mimic the ones produced by a nursing mom to calm her pups. It has proven to be helpful with this problem but was used in conjunction with desensitization so it is unknown if the collar or the training was the major factor in resolving the problem.
Her behavior concerning her mouth like excessive swallowing, lip smacking, etc is a sign of nausea which is often associated with anxiety and if she has nausea, she won't want to eat or drink. Often anxiety triggers an increase in bile in the stomach so pepcid might help reduce that behavior. You can give your dog some pepcid at .25 -.5 mg per pound every 12-14 hours.. Read about dosages and usage information here:
When she starts the behavior, ignore it as much as you can. If you know a storm is coming, crate her and muffle the noises with heavy blankets over the crate. This may help her be less anxious until you can complete desensitize training. You can also give her a special treat when she is crated like a peanut butter or yogurt filled Kong that you have frozen. She'll be busy getting the treat out of the kong and ignoring the noise especially if you muffle it.