How does trichotillomania feel?
Some people experience urges as itching, and some as pricking or hurting beneath the skin. Many feel like small insects are running around under the skin of the scalp or the rim of the eye.
Why can't they just stop?
Think lemmings for a moment; a tricster trying not to pull is rather like being a lemming, but not being allowed to jump over that cliff. You might always be compelled to do something, but that something doesn't have to be good for you. Trichotillomania urges are stronger than wanting to eat that cream cake, because you can walk away from a cream cake. Even a lemming can walk away from a cliff.
It's like having a magnet in your hand and the attracting magnet in your head, because your hand gravitates upwards without your say-so, some of the time.
The physical addiction to hair pulling is strong. Obsessions with searching for a root or selecting the right hair can be overwhelming and long periods of time can pass without awareness.
Tricsters find hair pulling soothing and comforting, it doesn't hurt and it's an occupation requiring nobody else's involvement.
You might need to accept that you can't change your child's behaviour. How will you feel if they continue to pull forever? You might feel as though you can't cope with that situation, but you would be able to cope.
It's almost impossible for anyone to understand unless they've lived and breathed it, but do try to be supportive. You're doing great, just by being here.