Is a 9rd old child's bedroom private

My friend has a 9 yr and a 5 yr old old daughter. The 9 yr old will not allow her sister into her bedroom at any time. She has become very violent with her phsically and verbally when she has gone in the bedroom. She has repeatedly told her she hates her and wishes she were dead. Neither of them go without and the 9 yr old doesn't seem to appreciate anything mum n dad do for her. She has a very low mood most of the time, shows little remorse or empathy, smiles little and is very negative about everything, she is a loner compared to other kids and generally prefers to be on her own with her horse toys or with my daughter who too likes horses. She only allows my daughter and one other friend in her bedroom (because they are her age and like horses too). We are going abroad with them soon and she is not the slightest bit excited about it. She says she doesn't want to go. My question is, if she says she doesn't want her sister in her bedroom, should that be respected? It is her bedroom after all! Thank you. My friends is at her wits end, the violence reaction really is taking its toll.

[mammo]

I think at this age it's typical for a 9 year old not to want their 5 year old sister in their room.  What concerns me more is her violent reaction, her down mood, being a loner, etc.  If I were your friend, I would get her evaluated by a child psychologist to head of what could become a worse situation in the future.

[smudgerecclestone]

Thanks mammo. My friend expressed concerns to the school nurse who said because she behaved perfectly in school, her work was fine, she never got in trouble, they didn't think there was a problem. She is painfully quiet apparently at school, TOTALLY the opposite of how she is at home! Thing is, she doesn't treat other kids or adults in this way so it makes me think it isn't a personality disorder, she knows when she has to behave! When she comes to my house she is perfect!