My 4 year old daughter has a habit of pulling her hair when she is tired

I have taken her to the doctors and they have told me 4 times it’s a comfort thing and she will grow out of it

I have tried literally everything I can think of to try and stop her doing it from putting oil in her hair to distraction and reward charts with no success😩

People keep commenting on it as the top of her hair is really short and it’s getting me down

My MIL even suggesting that it is self harm this one has upset me the most

Does anyone know why she could be doing this and what else I can try to stop her doing it

Anyone else ever experienced this ?