The inference seems to be the excessive amount of energy and time it takes to get your hair just right and so betrays self-absorption and self-consciousness. It is known from non-biblical literature of Roman times that any woman wishing to be seen as having a good measure of self-respect would not appear in public without her hair all done up. See also 1 Timothy 2:9.
3 Do not let your adorning be external the braiding of hair and the putting on of gold jewelry, or the clothing you wear