Welly might sound odd but is she on the pill?  I had to go on the pill early for my periods and man, one particular pill gave me really bad side effects. I was a really happy kid and just started crying and being really emotional over nothing, I knew I was being a dick and mum took me in and we got a pill change that helped but it is worth thinking about, sometimes the school nurse can put them on it without parental knowledge. Hormones are bad enough at that time let alone mixing synthetic ones in.  Also really quite serious about this start noting the moon phase when she is worse.  Full and new moon phases really do make a difference.  Sounds silly but its true, and new moon can be as bad as full.  Just random thoughts.