intrusive thoughts with self injurious behaviours

Good Afternoon everyone 

My topic is regarding my 12 year old daughter diagnosed ADHD and Autism strongly suspecting OCD.

My daughter has experienced horrific thoughts since she were 7 years old , these thoughts have always been put down to anxiety with her autism .

I have always questioned this anxiety as it is so so obsessive . An interest starts off as really calming for my daughter but after a short time the nasty thoughts start relating to the interest .

For example my daughter loved Elsa from frozen she became really interested in who Elsa were . To begin with this interest was ok but after time the interest became obsessive and she started to have horrific violent thoughts over this character  that started a spiral of harm thoughts to herself . My daughter was constantly scared  she hurt some one and would ask repeatedly did I hurt you I'm scared I hurt you , . Then she say I'm scared what i searched up in the past ( she hadn't searched anything inappropriate up )

Other cycles include ... Interest in a particular number again interest starts off ok , then after short while she wants to control everything with this number eg gets incredibly angry if im brushing her sisters hair at this time . Along with this need for control she develops this nasty character in her head who she says is controlling her and  she wants her to shut up leave her alone. Believing her sister is prettier than her and to reassure herself she would stand Infront of her sister staring at her face  and this would happened several times a day .

Over time these interests would change and again start off nice then the nasty thoughts would drip in and take over bringing in a nasty character in her head .

We are going through another cycle now which involved a boy who she developed a crush on . Again to begin with this friendship was ok but then the nasty thoughts crept in having her believe  that other girls were prettier than her and she is ugly . To combat these thoughts my daughter started to follow this boy around school would scream and shout at other girls who went near him , She started to say this boy belonged to her and kept trying to get to him trying to break through doors jumping out of her school transport bus (luckily it was not moving )

To combat these nasty thoughts my daughter has tried to self harm punches her head constantly looks for reassurance .

Has anyone any similar experience and any coping strategies ?