Como dizer "autocrítico" em inglês

Another tack, a bit more colloquial would be
Ela é uma ótima pintora, mas é muito autocrítica, nada que ela faz nunca está bom

She is (extremely/very) hard on herself, hard on her work, she is never satisfied with her work at all.

She is very hard on herself; she should let of her "inner critic" a bit, it doesn't allow her any imperfection, most of them no one would notice!