Zebra Finch, Respiratory Infection?

I've noticed recently that when my Zebra Finch breathes, she makes a clicking noise. I can see that her beak is slightly opening and closing which is causing the clicking. She also seems to be swallowing ALOT and sort of like gagging. This happened when it started to get cold outside so I thought it might have something to do with that, but since I've put a heater in my room I keep it no lower than 70 in there, yet she still does it. Could it possibly be a respiratory infection? I thought I saw her sneeze today, but I'm not sure (no discharge came out and it was silent, her head just moved in a sneezing manner.) She's active, eating, drinking, beeping (though her beep is sort of squeaky now) so I don't want to take her to the vet unless it seems like something serious. And no... I'm not the type of person that won't take an animal to a vet just because it's too expensive or too far away (the closest avian vet is two hours from my home.) It's just, earlier this year she had a tumor removed and she didn't take well to the drive there and back. She was pretty scared. I just don't want to put her through any unnecessary stress but at the same time, I don't want anything to happen to her and me be the cause of her possibly dying. I'm asking here first because I don't know if I'm just paranoid ever since she got that tumor, and now I think she has every disease in the book... or if these are signs of a respiratory infection. I really love her and don't want anything to happen to her, so any help is appreciated.