She seems much better, thank you all! Fingers crossed the weird sneezing/coughing/choking doesn't come back!
It did also occur to me - OH is an artist, and the day before was treating a new palette he had just made with linseed oil. Not that linseed oil is poisonous, but it does smell very strong, and Poppy started the sneezing/wheezing/choking after I got up and opened the door to his studio... At any rate, I have asked him only to use that out in the garage or the garden in future, in case she had a reaction to it.