My daughter had the same problem at around that age, and her pediatrician told us that often little girls (CAH or not) have mild fusion of the skin by the opening of the urethra. I seem to recall that it had something to do with a lack of estrogen at that age, but don’t remember what she called it. Dd’s opening looked a little smaller than normal to me, and we were concerned that urine might pool there and cause an infection. Anyway, she gave us a prescription for an estrogen based cream called Premarin, which we applied to the area a couple times a day. You could almost see the area "opening up" with each passing day! After about 4 weeks, the skin completely "unfused" and she’s had no problem since. I do also recall the pediatrician saying that some girls need to do this sort of treatment several times during their childhood, but she really did impress on me that it was no big deal, quite common, and that Dd would definately outgrow it when she got closer to puberty and started producing her own estrogen.