Why does daughter still have mongolian spots on her back?

Can fade with time. Mongolian spots are bluish markings on the skin, normally on the lower back, often noted in the newborn period. Mongolian spots are common among darker skinned persons, such as those who are of asian, east indian, and african descent. They can be mistaken for bruises. They often fade with time and are usually gone by late the teen years. They cause no complications and do not need treatment.
Can persist for life. These patches have skin cells that produce more pigment, creating the tonal difference. They may fade some as the skin thickens, but many persist for life.