Another thing that works great is a tight shirt on the dog. There is special one made for dogs called the thundershirt I think. I know many people that swear by them and use them not only for storms, but anything that makes the dog anxious or nervous and it really helps calm the dog.
Your vet will probably give you a sedative, aceopromazine is one that is commonly used for thunder phobic dogs. It can really knock some dogs out depending on the dose, but usually they are just calmer and able to relax. Trust your vet on the dose, but if whatever they give her really knocks her out talk about changing medications or a lower dose. Sometimes just being out is the best option for the dog though.
Other things that can help, talking in a low soothing voice, rubbing the ears slowly and full body strokes that are slow. All of these can help be calming signals. She is probably too worried, but yawning at her and blinking your eyes may also help, is she will start blinking more or taking deep breaths it will help calm her down too. You can teach those on cue with some work and then use as needed. Also when were is no storm, teaching her a safe place- kennel, bed, etc that you can send her to and she can learn to relax there. Let me know if you want to know more about that. Those are things that are long term though and having a medication can really help for now and as long as needed during storms. The others are some training that can help in general.
Growing up our golden retriever was terrified of storms too. We did medicate her a few times, but usually just let her sit close- she could still eat and function, was just very nervous.