I don't know how to treat/talk/handle her at the moment and I feel so 
She's 8 years old. The eldest of 3 children. She is doing very well at school and is very well behaved, in fact she goes out of her way to be nice to everyone and it is commented on. However at home she is such a different person
. I don't know what we are doing wrong 
She's moody especially if she doesn't get her own way. Refuses to discuss anything by storming out of the room mid conversation. We have tried to be calm but her behaviour is bringing the whole family down.
She sees the downside of everything. We are about to go on holiday, she doesn't want to go. She can't really give me a reason, just is fed up of everyone saying she'll have a nice time.
She wants a hamster, we went through this last year with guinea pigs - she got them, she now wants nothing to do with them and when we pointed this out to her she promptly went upstairs and wrote a for sale sign for her guinea pigs. She's not getting a hamster, she won't look after it. We've tried to explain this to her but she ended up throwing her purse at her dad and stomping off screaming.
She goes riding and wants a horse. We can't afford anything like that but we can afford lessons for her. When we point this out this will send her into a sulk and a stomp, accusing us of being horrible.
And then 10 minutes later she appears downstairs sweetness and light, full of apologies. It's like someone has switched her for a different child.
Help 