However, since then, we have been aware of her rapid breathing. Maybe it's always been like that, and we only noticed because we were paying more attention, after that problem. Recently it has seemed to be really noticeable though - she doesn't struggle in any way to breath, no flared nostrils, no discharge, eating well, active, happy... just simply the rapid breathing, which is quite visible as it rocks her.
When she and Dijon were sleeping, we counted their breathes for a minute - 38 for Dijon, 90 for Mabel!
We saw the vet this afternoon, who thinks that she has chronic mild pneumonia, something she will probably have to live with, and hopes to manage it by keeping her away from dust, and daily dose of antibiotics - Karidox (Doxycycline) 10mg/ml, 0.08ml per day (should be easy to disguise in food!).
Hopefully this should prevent the coughing/sneezing returning, and the breathing should calm a bit.