How awful for your DD! Perhaps reassure her that because they are too cowardly to say anything to her in real life, then they are going to be too cowardly to actually do anything! I know it's not much, but it might make her feel temporarily reassured.
I had a similar thing happen to me when I was at school, people writing things such as "just slit your wrists and make everyone happy". That turned out to be one of my "friends" so I wouldn't rule out her friends - especially if no one has said anything to her face and it is all just on the toilet wall.
Good luck getting through to the school - in my experience it is hard work trying to get them to take it seriously. Hope everything sorts itself out soon.
How awful. It is a horrible thing to go through and I hope it is short lived.
My advice would be to consider whether the culprit might be one of your DDs friends. Her friends will know which toilet she uses. One of them may be (secretly) very jealous of her. Has one of her friends not been doing as well in class recently or perhaps your DD is better at sport or art. May be she isn't as popular as your DD, but wants to be.
In my experience the school will most probably question those already known to them as 'trouble makers' or those they consider to be likely candidates for such behaviour. However, they tend to overlook the possibility that friends can sometimes be responsible for such nasty behaviour.
What about the handwriting/drawing on the wall. Is it disguised or does your DD recognise it?
Nasty messages written on a toilet wall? Including comments Wishing she was dead and should kill herself.
This is so disgusting, we are fuming. She is a popular girl and has never experienced bullying of any kind before this. No-one is unkind to her face but a few messages have been written on the toilet wall.
The no1 suspect was off today when an additional incident occurred, which rules her out.
School don't seem too worried and have said they think it was just a 'joke'. It is certainly not a joke having a dc terrified to go anywhere alone as she thinks someone wants her dead.
Head has been copied in to all Communications but at the moment they are 'investigating'. I personally think they should tell all the children that the police will be involved to scare them and get someone to confess.