I think Esme has some sensory issues. She doesn't like wearing clothes to bed and Sarah has said that it's hard to buy clothes for Esme as she doesn't like the feel of most fabrics, especially jeans and sweaters. In very old vlogs I remember Sarah saying they had a lot of "trouble" with Esme growing up and she missed out on a lot of school as she was "ill" and that's why she's so far behind in school. She never elaborated and to my knowledge hasn't addressed this again apart from saying passing comments like "Esme learns differently." Maybe she has high functioning Aspergers/Autism, I don't know for sure but it would explain a lot of her behaviour, whatever it is I hope she has the help in place to make things easier and that her parents are supportive, but of what we know of them I highly doubt it.