You're so fortunate to be able to contact the foster mother and receive good information like this. There's a lot here to sort through -- all those puzzle pieces you mentioned that can take time to work through. Herpes flare-ups are possible. (We're pretty sure we saw those in our previous cat: she sometimes had a day or two or three with weepy eyes and some sneezing.) And food (even just one seemingly small ingredient) really can do weird things to cats even if they're eating well and using the litterbox without any problems. Do you happen to know/remember what she was eating before she started to have symptoms? Also, I know this is an old topic, but what kind of kitty litter was the foster mother using? (I sometimes think about "reset" as a good starting point for certain things even if those parameters and products aren't perfect.)I actually messaged her foster mother last night to ask if this has ever happened before. She fostered Kila for about a year between when she was born and when she was adopted out the first time, and then again for a short time when her first adopter gave her up late last year. She said Kila experienced something similar to this once before, when she moved homes the first time, and that it was cleared up with Clavamox and Lysine. Possibly a herpes flare-up? She also thought it might be food related (apparently Kila's been eating pretty low-grade food her whole life) though I'm not sure about that. She really likes the grain free turkey food we give her and her appetite and litterbox habits have been great.
I wouldn't be surprised since they often go together. Here's a page on allergic asthma in humans. And a search of "allergic asthma in cats" brings up a lot of results (though some repeat), including the beginning of a (paywalled) article that says some cats don't respond to the usual treatments. Which makes me wonder about the steroid itself and what She's a witch mentioned about dosage. (FWIW, I think allergic asthma is likely what Ireland has; I seem to recall that the vet mentioned that possibility, too. We may never know for sure, but given her habits of sniffing at the floors, I think dust and/or pollen is likely at least part of her problem and of course all that stuff floats around and accumulates together.)Or maybe it's allergy related and the asthma is only part of the full picture?
I hope the vet is helpful tomorrow!