。
She deserves to be scolded.
Literal
She [topic-は] scolded [naturally-て当然だ].
叱られて当然だ literally means 'being scolded is only natural.' 叱られて is the passive te-form of 叱る (to scold), and 当然 (とうぜん) means 'natural/deserved/of course.' The pattern ~て当然 expresses that an outcome is the expected, justified consequence of someone's actions — whatever she did, the scolding is a fair result.