。
She is always unfazed by criticism.
Literal
She [topic-は] always criticism [by-に] is-not-shaken.
動じない (どうじない, 'unshaken, unfazed') is the negative of 動じる ('to be moved, to flinch'). With 常に ('always'), it describes a consistent character trait. The に marks criticism as the potential trigger that fails to affect her. This stoic composure (動じない) is often praised in Japanese culture.