Hi,Welcome to HCM,
It seems that your mother is suffering from Allergic bronchitis
She requires some investigations like,
1,X ray chest,
2,complete blood count
After reports go for treatment accordingly.
She might have Eosinophilia
which gives similar problem but with simple medicines like Di ethyl carbamazine (hetrazan) she will become alright.
Avoid fried and junk food,
Avoid allergen if she has doubt about some food stuffs.
Do some deep breathing exercise
Ok and bye.