PLEASE get your bird to a vet. Look on the internet for any Parrot Rescue organizations in your state. Contact them and tell them about the situation, maybe they have someone there who can help you get transportation to an Avian Vet. A regular vet could help you too, as many have experience with birds even if they are not Avian Certified. Your bird has been on a very poor, fatty diet if what she has had is mainly sunflower. If she has been eating that for her whole life it will eventually kill her. Amazons can live to be 60 or 70 so at 23ish she is still young! Most seed diets are not good and Amazons are prone to obesity and liver problems. Does your bird get any exercise at all??
Try a variety of pelleted food to see which one your bird likes best. I tried Scenic Jungle Apple or Mixed, Harrison's and Roudybush before my bird took to the Scenic. She likes it because she can hold it in her claw while she eats it, the way she used to eat peanuts when her 1st owner fed her that junk! You need to slowly transition her by mixing pellets with seeds or try offering only pellets in the morning and see if she will try them. If she is not eating any, you can always give seed later but please try soon!! Also, fruits and veggies are very tempting and healthy so offer a great variety: carrots, pumpkin, cooked mashed sweet potato or yam ( my bird LOVES this), kale, sugar snap peas, blueberries, raspberries. NO NO NO Avocado (poison!)
Good luck and I hope you can find a vet ASAP. What state are you in?