Is her head swollen? Is she eating and drinking? Does she have a runny nose? She could have an upper Respiratory infection, You might want to separate her so no other chickens will catch it. It's happened to my chickens before and I put some oxytetracycline in the water it helped a lot. Good luck!
Where the sneezes dry? She could have a respiratory ailment going on. Sometimes things do get inhaled by chickens too. I would keep up with the Tylan for one week and if she does have something respiratory going on, it should clear up. If it continues, it could be some sort of fungal infection in the lungs, not likely gape worms, but you might get her wormed if it continues. Lung or gape worms in the trachea can cause rattling and wheezing.
Let us know how she does after this round of Tylan. I hope she improves soon!