My DBF's niece is in this situation : She "developed" before she was 10, when she was about 4' 10" and 105 lbs . Today, she is going on 19, and stands 4' 11 1/2" and about 145 lbs. There are worse fates than being a grown women less than 5 feet tall...But I think your friends were wise to let their daughter get a a few years older before letting puberty "freeze" her at a particular height.
Darn it-I meant to ping you to my remark above, re: the 8 year old girl beginning to develop.