Just picking up about the MH issue, its not correct that the police are the service needed if someone is a risk to themselves or others due to a MH crisis
That is a health matter and you'll have heard, if you've needed to phone 999 or 101 recently, a message saying exactly this, if you are in a MH crsis put the phone down and contact health services.
Obviously it may not always be clear if its a MH crisis that someone is having if someone is lunging at you with a knife or being verbally abusive/intimidating you and then you'll call the police obviously but ultimately its a health matter
In this case, it would have been far better if the parents had gone to collect their daughter, again Im not sure why the police are being used for things like this.
I wonder when more detail will come out about the wider context