Welcome to HCM,
After going through your daughter's history she has asthma
and recently suffered a chest infection
, post infection her asthma may have worsened and requirement of anti inflammatory and bronchodilator
drugs may be increased hence she is more breathless during exercise and there may be component of exercise induce spasms.
She should monitor her condition with a instrument called PEFR meter with the help of chest Physician and treatment can be modified accordingly she may require a course of oral cortcosteroids for this acute episode.
Please do not worry she will improve soon.
Please continue preventive medicines and worsening can be treated easily and this is the nature of the disease to have acute attacks and then remission.
Please take care