LBBB is an ECG finding only. One needs to try and rule any underlying structural abnormality in the heart. An echocardiography is certainly indicated. If she has no symptoms and it was only a chance finding nothing much needs to be done. However repeating an ECG once in a year is desirable. If the echo shows normal heart function and she has no symptoms the best thing is to take it easy. In case she has symptoms like shortness of breath or giddiness or effort related symptoms she needs to see a cardiologist.