Why did my wife have such a severe asthma attack?
Your wife has had asthma for a long time and was not on preventive treatment. Salbutamol is only a temporary reliever. She had a life threatening asthma attack which may have been precipitated by a severe allergy or infection. The right thing to do is to keep her on a regular preventive inhaler which has a combination of steroid and long acting beta2 agonist lifelong. Once she is stable she should get her lung function test done to confirm that her lungs have reached a stable state. Then her treatment can be tapered down but only under supervision of an expert. She should remain on the minimum maintenance dose lifelong.