Sorry to hear this.
My ds ,just 18, also has had debilitating ocd (intrusive thoughts) from the age of about 15.
He's had 3 courses of CBT and is now on an SSRI which has not worked so far.
What I've learned - try CBT therapy again (in our experience, unless your child is suicidal they won't make the criteria for CAMHs). Go private or through a charity such as Young Minds.
Call your local NHS mental health 24hr helpline if she's really struggling - can help to talk to someone different.
Download Headspace app and listen to some of the meditations.
Distract where possible - baking and tv have been useful here. Have the radio on in every room to 'drown out' the noise in her head.
Write down the worries and have a designated 'worry time' for a timed 10 minutes to go through them.
Wear an elastic band in wrist to 'snap' when thoughts are bad.
Download a thought CBT App - where she can write down thoughts and feelings behind them.
Speak to the welfare lead at school for a time out card, any other support and to make them aware. Do this asap.
See your GP for advice / to check bloods etc.
Read Parenting Mental Health - invaluable.
Hope this helps.