If there is no avian vet near you (have you checked "exotics vet"? sometimes they're labeled that way), then you might have to do your own research in tandem with a good regular vet. You can also check with local zoos or wildlife reserves to see if they have a vet on staff that could help you or know of one.
Please look up "budgie respiratory infection" on YouTube and evaluate your budgie's breathing and tail bob versus the ones that you see on videos. Also, you can listen to your budgie's chest to see if you hear a clicking sound (the heartbeat is very fast, but this would be something different).
Also familiarize yourself with the signs of budgie illness and see if yours is presenting these symptoms. An ill budgie will mask the illness until they can no longer do so, which means they are very sick by the time you get them.
You will also want to keep your budgie very warm by putting a heating pad or hot water bottle on half of the cage. They puff up to try to raise their body temperature when cold or ill. You can also run a hot shower and with a few drops of eucalyptus oil so that the steam helps her breathe easier. Keep her energy up by offering lots of millet and water, which you can even soak in Pedialyte to keep her hydrated. If her droppings are small or have a dark green stain around them, it means that she is becoming dehydrated and needs help quickly. Keeping a record of her weight can also help you determine how she's doing.
Lastly, it's normal for a budgie's droppings to become a bit runny when they are stressed (such as when they come to a new home or go to the vet). If they return to normal quickly, it should be dismissed as stress. If not, you will have to diagnose the problem.
You can also find out how to assemble a budgie first aid kit here on Talk Budgies so that you're prepared for the next problem.
I hope that these suggestions help you if your bird is ill. However, I can't stress enough the importance of research alternatives to avian vets in your area. It's the first and most important part of the budgie first aid kit.
Good luck and we hope that your budgie recovers quickly!