Hi! Asthma is the first thing that comes to mind... I always kept my cats away from smoking guests for this reason ( they were long haired cats at the time , more asthma prone than short haired ones)!
I had one with asthma, she sneezed and whistled a lot and was on madication, theophylline daily, and the equivalent of Ventoline,in a spray form. However, since you CANNOT spray a cat in the face, there is a canadian device that allows you to spray from a distance ( like a long tube, so the cat doesn t hear the pscchiitt!!!)
I would also have her heart checked. Sometimes sneezing and problematic breathing are heart related.Especially in older cats. best of luck and... Try and smoke away from her, in either case!
He might be developing asthma. I am sorry you smoke.