I agree that you need to have along talk with your vet. Something is wrong if she keeps getting worse. She may need some type of specialist. If it was just a birth defect you think the damage would be done and that is that but if she is getting worse then I would also be very concerned. Has she been
x-rayed. I'm sure she has but just thought I would ask. Maybe you could contact the vet university and ask some questions about cost and what they would be able to do for her. You wouldn't have to take her if you didn't like their answers.
We are praying for little Amy and I hope you get some answers soon. You are included in my prayers because I know how worried you are and just how stressful that can be. Hang in there and let us know what you find out.