You need to get your daughter in to see a psychiatrist right away. It sounds like she has several things going on, and only a specialist can tell you what they are. Good luck and take care.
I've tried but she is refusing I've also tried saying we're going shopping but she knows i'm lying it's hard.
Well, she needs help. So, since she is refusing - she can chose. Either she walks into a psychiatrist's office like the young woman she is, or you have her hauled away like an animal to a mental institution and held there against her will. You can call the authorities and have her hospitalized because she is a danger to herself since she is hurting herself. While there, she can enjoy the loss of everything her life is now and be forcefully put on medications. OR, she can go to the psychiatrist and have mature discussions about what the best course of action would be to help her.
My husband was taken off in a paddy wagon to a hospital as a teen - I've heard the stories, I wouldn't recommend it (and he wasn't even depressed or a danger to anyone). When I was depressed, I chose the psychiatrist and I don't take meds - I just have regular counseling sessions and it's helped a lot.
She says there is nothing wrong with her and that what she does is normal but she threatens her self and her brother with a knife??? Is her behaviour psychotic??? I am scared to do those things because what if she hurts me? Or even kill me? She will proberbly kill herself that's the main thing I am affraid of.
I'm not surprised that she says there's nothing wrong... but she's 15 and she's your child. You need to get her help one way or another. That's why I suggested giving her the choice - she may see things differently if she knows she will be getting psychiatric treatment, even if it is against her will. Don't give her so much power in this situation. Don't be fearful of her, she is ill. Just because she's threatened her brother with a knife, doesn't mean she'll actually use it. And if she tries to hurt you, stop her! You have more control in this situation than you're willing to admit. Give her the choice and if she becomes violent, defend yourself. In a hospital, they take every precaution they can to ensure patients cannot kill themselves while there. Not getting her help is much riskier - for her and others. Without help, she will have a much higher chance of harming herself and plenty of opportunities to do it. Since you have so many doubts, you should contact someone in the mental health profession to discuss this. Depending on where you live, there are urgent care centers exclusively devoted to mental health issues, state mental health services, etc. I will tell you that they will recommend her being seen immediately because of the threat to her and others.
Of course she says this is normal - to her, it is. Maybe some of her friends are going through similar things, but she doesn't see that this doesn't happen to most people. It doesn't help any that it's quite popular these days for teenagers to feign these symptoms - I couldn't even begin to tell you how many kids my daughter goes to school with claim to have been cutting themselves (to find that it's only marker) or who constantly use suicide threats to manipulate their friends or discuss violent/morbid ideas - even kids who claim to hear voices. It's similar to a trend from about 15-20 years ago where every kid said they had ADHD because they hated homework - now every kid says they're depressed or bipolar because they think people will respect them if they fear their self-diagnosed "mental illness". The problem is that most of these kids have nothing wrong with them (except a severe need to get attention) and it hinders the chances of kids who are really ill getting treatment - partly by convincing kids with genuine illnesses that their situation is normal.
Your daughter does, indeed, need psychiatric treatment. I truly cannot tell you if she is psychotic, only a doctor can tell you that. But it sounds like she is genuinely depressed and that it has been getting worse for a long time. While she may not be "psychotic", that does not mean she is not mentally ill. There is no reason to not get her help - ESPECIALLY since you fear her causing harm to herself and/or others! You are the parent in this situation and you have every ability and right to get her help - even if it has to be against her will. Do what you will, I can't make you do anything either way, but my opinion is that you need to get her help.
Thanks I'll get a psychiatrist to come to our house so she can be delt with there and then but if she gets angry that i've done so i'll have to call the police to get her into hospitalization asap It will hurt me that's she's gone but deep down it's for the best thank you so much :)