8-yo DD is out of control and I do not know how to handle her!

[runningLou]

DD is 8 but is showing behaviour I did not expect before the teenage years. She is incredibly rude and unpleasant to DH and I, regularly storms out of rooms in a huff, slams doors, hits furniture etc. In the past few weeks she has been having meltdowns several times a day - she will get into a disagreement with us about something (e.g. I want black walls in my bedroom / I will not eat breakfast) which will lead to a screaming tantrum and her saying some horrific things - we don't love her, she's not part of the family, we shouldn't care about her ...
I am really, really struggling to parent her right now. I have been in touch with school as I think the root of the problem is bullying and peer pressure. There have been no other triggers at home in terms of changes in the family. I have also been in touch with a child therapist who gave me some suggestions about rewarding good behaviour and sanctions for bad but I have not really been able to implement them as DD just uses these as a provocation.
At the weekend she threw out her diary and said I could read it before binning it. It detailed some bullying incidents at school. I am going to request a meeting with the pastoral lead at school and I would like her to move classes to get away from the girl in question.
Am worried though that I am focusing on school when the issue is her behaviour at home. This morning she had 2 screaming meltdowns before breakfast. She reduced me to tears and I was sobbing in front of 4 yo DS. I am ashamed and guilty but this is ruining our family life.

[MadSprocker]

It sounds like the bullying is the catalyst to the behaviour, and she is taking it out on you because she knows you love her. It sounds like a meeting at school is the right thing to do. Will she talk to you now that you have seen the diary? Hoping things get better.

[KingLooieCatz]

I couldn't read and run. It sounds like a huge clue that she offered up this opportunity for her to read your diary, perhaps she needs you to know that she can't cope with what is going for her but it is too difficult for her to talk about. It might be that once she knows she has your support to tackle things at school, and hopefully things start to change at school, the behavior at home will improve.