User - the girl I know tried to get her younger siblings removed into care by making false allegations. The family spend throusands in legal fees trying to protect them, they got into debt to fund it.
They had already spent thousands trying to get therapeutic help for her.
As soon as her first sibling turned 16, she started harassing and stalking him. He can't go to the police because they know it will set off the attacks on his parents and younger siblings again. They all live in a constant state of fear and anxiety and what she will do next.
Random is right about protecting yourselves. This couple will only meet their daughter in a busy public place and will only correspond by email. It's a horrible situation to be in but they have to protect their younger children.
People who know nothing about the situation judge them.
They say things like " she's ill, she needs medical help " . But don't say how you can force an adult to get help.
Also she is not ill, she has a personality disorder. Very few psychiatrists or psychologists will work with people like her as they are very hard to "treat" , even if they do want help.
This type of abuse isn't illegal ( most of the time ) , the police can do nothing.