FGM needs to be eradicated alltogether full stop. But waiting until the girl is 18 so that she can make her own decision is a first step in the good direction.
"Recently some progress has been made towards eliminating FGM, by addressing the women that actually perform the ceremony, the sowies (initiators). Many have agreed to stop forcing girls below the age of 18 to undergo circumcision. Also, in some parts of the country they've consented to give it up as altogether if provided an alternate source of livelihood."