she is showing early signs of puberty, so I'm assuming there are hormones in this mix too.
Some days she is lovely, today she is a wreck. A friend came round after school today, before they went off to a club together. This school friend is a show-off, I'm-so-much-better-than-you-type, always bragging, over-dramatising or talking in a sulky voice about something. When I picked them up from the club, the person running it said my DD had had trouble controlling herself and had been crying over very minor things. I'm going to ring this woman again later for a proper chat - couldn't get too many details just now because the number of flapping ears was causing turbulence!
Fairly normal at this age, if my just-turned-9yo ds is anything to go by. I think they need their emotions accepted and not criticised, even though it drives us nuts. The school friend could well have made her feel small, which, together with being tired, could hve set her off.
I don't mean you're criticising her, but that she needs to hear from you something like "You seem tired. Did you have a tough day?" rather than "Oh stop being silly" or "Behave yourself!" (which my ds hears far too often from me ).