If the minor is over 16, she can marry with both parents' consent, if the parents live together. If they are divorced, separated, or one is deceased or unavailable (out of state), then the parent having custody of the minor may consent. It does not matter that the minor has a child (under Georgia law, may be different in other states).
I am exclusively a family law attorney, practicing primarily in the metro Atlanta, Georgia trial courts. However, I handle appeals from anywhere in Georgia.