It is definitely age related, but if its way over the top you might want to bear this in mind - my own DD - also 9 suddenly got really bad - the strops took on a far more sinister feel - more like complete hysterical meltdowns - scarily so :(
Thankfully (sort of
) I had seen similar behaviour in her before & knew it to be linked to bullying - she wasn't telling us anything like this initially, she didn't the first time round at 7 - but I had my suspicions & it turned out to be spot on - even though her very OTT strops could be about ANYTHING, from what she was going to wear, how her hair was, food, tidying her room, not watching a TV show, us not getting a Dog also came up - ANYTHING had her go into meltdown
thankfully the School have worked with us, as did the ring leaders Mum & the problem is mostly resolved &DD is back to her old self - strops yes, but NOTHING like the scary way she was
The Head pointed out to me, that this is the age all the politics kick in with girls - I expected a bit later as it was when I was younger, so it took me by surprise
- but she was right, DDs group of solid girlfriends she's had since nursery, suddenly, almost overnight, turned into a gang of loud, bossy, I'm in charge & you follow my lead or you're ostracised prima-donnas - several vying to be ringleader & DD just wasn't having any of it, didn't want to be involved with the bitching & back biting, so she was set upon by the group
Might be worth having a chat with your DD about how things are with her friends, or just generally girls in class ( DD was upset her friends were picking on others in School too) & generally keep an eye on the dynamics between your DD & her group of friends if you get a chance to see them all together - I was shocked with some of the stuff I witness, girls who only weeks earlier had been the sweetest, most polite, being very devious & nasty to other weaker members in the group