Kath, I developed really really early, by the time I was 8-9, I had 12c bra size. I had all physical changes barr 1, i didnt actually get my period till I was 16!!
All the girls at school used to gang up on me and abuse the crap out of me when I was 12 saying that I already had my periods, and was lying just because I was more developed than them. Even to the point of holding me against a brick wall, and stretching my shirt back so they could all see how big my bust was.....I always felt so dirty, and abnormal, and a freak.
Years later, I found out I always had PCOS, and that was the explanation.
It can be so hard going through hormonal changes so young, especially when your friends arent, and you have noone to talk to, or noone wants to listen to you, or believes you.
I would suggest maybe looking at a counsellor for her, as she has probably got some issues that she just cant get out with anyone.