Your daughter needs to get annual checkups done with a pediatric cardiologist.
A murmur is always abnormal and indicates an underlying heart dysfunction. Hence it needs to be checked for at regular intervals. The cause of the murmur is to be identified and treated accordingly.
do affect the growth and general condition of a person as it predisposes to infections and other conditions.
Valvular heart diseases need to be ruled out and these may require antibiotic prophylaxis
Hope this helps.