She could have a viral infection that comes back for any sort of stress reason.
You can read about upper respiratory viruses here
http://marvistavet.com/html/feline_upper_respiratory.html
You might ask your vet if the x-rays show any possibility of asthma. You can read about this here
http://www.cfa.org/articles/health/asthma.html
Sinus issues are listed as a possible problem in the breed here
http://www.petmedsonline.org/cat-health-scottish-fold-breed.html
And a fungal infection such as aspergillosis is a possibility too
http://www.peteducation.com/article.cfm?c=1+2134&aid=232
You may need to do more testing and as cash flow is an issue you might check out Care Credit If you qualify this may work well for you.http://www.carecredit.com/A credit card company for health care, including veterinary care."With a comprehensive range of plan options, fortreatment or procedure fees from $1 to over $25,000, we offer a planand a low monthly payment to fit comfortably into almost everybudget." They have a zero interest program if you pay within a certain time frame and they list the vets who work with their product.
Hope this helps you!
Cat Health, Behavior, Care Expert
30+ years cat owner, rescue, breeding, study of behavior & health care
You might try some Feliway cat appeasing pheromone with her to calm her down.
You can read about this here
http://vetmedicine.about.com/od/behaviortraining/a/Feliway.htm
and all sorts of sites and stores an vets carry it.
Feliway can be sprayed in the cat carrier too if you get the spray bottle.
You might consider a home visit vet if there are any in you area and this site may help you find one
http://www.vetlocator.com/housecallvets.php
If she is easily stressed it could be the upper respiratory infection issue as stress lowers the immune system.
Thanks for the above accept!