My dog is having a tough time with asthma.?

I found my sweet "pound puppy" on my local animal shelter's website. I was so excited, she was exactly what my parents would let me have. She is two now and I love her so so much. Gracie has caused a lot of problems (two attacks on other small dogs), but she has a great heart. This winter, she battled over and over against pneumonia, and may have scar tissue, which is causing shortness of breath. She may even have a chronic lung disease. My family can't afford all of the bills, so we took her today to the veterinarian office for the last time. She was given an asthma shot at the office, mainly because she experienced her worst asthma attack yet. Medication has been given for a week, but if it does not work, we may have to euthanize her. I am ultimately heartbroken. I know she is suffering, but have any of you been through something like this? Can surgery fix it, and if so, are there charities out there that would help? Thanks for understanding.