Thanks for the thoughts. Luckily she doesn't have a problem talking to me about periods, puberty and everything else. She knows we've got a stock of teenage-sized pads and have had many chats about it. But while I can tell her what happens, I can't really tell her what it feels like or what emotional changes she might experience because I don't know what that's like from the inside.
All that being said I did sit down with her for half an hour last night while her brother was out and talked about this some more. From what she said, I think it's being triggered by tiredness which is why it happens at night-time. But I think the causes are several - hormones being one but I think issues surrounding her unreliable mother are playing a big part.
I suggested she keep a diary of when she feels like this and what thoughts are coming in to her head and then we can talk about it again. I also suggested she have a chat with an old family friend whose 14yo DD my DD gets on with very well. I think if she can get some reassurance from other girls that this kind of mood swing is normal then she (and I) won't fret about it.
Talk to her yourself. Just be honest and open and give her a big hug afterwards. She'll be asking you to buy her tampax with the weekly shopping one day so best not to make this something she has to talk to someone else about.
Has she started to develop/ started her periods? sounds hormonal to me too. Have you any concerns about her struggling with school work? Do you have any female family members or friends that could chat to her about how they feel with hormones to reassure her?
DD's 11 and, generally, is lovely. She's been a bit moody at times but that's not a big deal.
What's concerned me a bit more is that she recently told me that she frequently finds herself very teary at night time. She said that she often finds herself crying in the shower, either out of a feeling of frustration or just general sadness. She says that it's sometimes linked to something trivial that's happened but often she's got no real idea of what's going on.
She's normally very much an open book when it comes to what's going on in her life (it's often just getting her to stop talking for long enough to draw breath that's the tricky bit) so I don't think it's anything like bullying at school.
My general suspicion is that it's mainly pre-teen hormones and not something to worry about but does this kind of thing ring any bells? I suggested she keep a diary of when it happens and how she's feeling to see if she can spot any pattern. Any other ideas of what could help? I'm a dad so the whole pre-teen girl thing is rather new to me.