: CBBE replaces the "FemaleBody.nif" file for adults; children use separate assets that aren't overwritten by standard CBBE installations. Community Guidelines
To maintain a stable game environment when enhancing character visuals: fallout 4 cbbe child body better
If you only want to change the player character's body (if playing as a child) and not all NPCs, you should use the Unique Player and Followers : CBBE replaces the "FemaleBody