My Topper is almost 12. When he was 2, he had really bad pneumonia, tried several different antibiotics and had a bronchoscopy with cultures to identify tha bacteria. Then another 6 weeks of medictions. Several times over the next 3 or 4 years he had it at least once a year, we spent 2 years giving antibiotics one week out of 4, then he went several years wtih no problem. A couple of years ago he had pneumonia again, then this year he started wheezing and coughing and we were back for another bronchoscopy. No pneumonia, but chronic asthma for which he gets a bronchodilator twice a day. He coughs at bedtime, in the morning, and with exertion, but he is living a good life and able to run a bit at the park, though one lap and he is done. The specialist indicated that this is not all that rare a condition for dogs and cats.
But that first pneumonia was hard to cure, I'm still not sure we really got rid of it even after 6 weeks of the correct antibiotic. Hang in there! I think our heat and humidity encourage bacterial growth and make it harder for our guys, I know Topper breathes better when it is cool, the heat this summer was very hard on him.
Good luck with your girl, hang in there !
Anne in Tampa