My mother has asthma attack all the time though she is taking 7.5 mg of predesilone daily. now she has flu and feeling cold more recently.?

Not an easy question: Though oral steroids are sometimes used in treating asthma's more severe cases, please be sure that she is taking her inhaled steroids and rescue inhaler properly. This is often an overlooked problem in uncontrolled asthma. There may also be a very strong trigger in the house (pet, etc) that may be a cause. If she cannot use inhalers, she may be a candidate for nebulizer administered meds.

Treat the flu: She is more susceptible to infections because of the chronic steroid therapy. Make sure she treats the flu if that is what it is, or the uri/bronchitis. Have her see a specialist. There are other treatments but Prednisone for asthma, and if those have been exhausted or not working, she may need more of it, at least in the short term.