。
She blushed when she saw it.
Literal
She [topic-は] that [object-を] see [and-て] face [object-を] reddened.
顔を赤らめる ('to blush,' literally 'to redden one's face') is the literary/written verb for blushing — slightly more deliberate than 顔が赤くなる ('one's face becomes red') and far more compact. 赤らめる is the transitive form of 赤らむ ('redden') — 'cause to redden,' here applied reflexively to one's own face. The whole phrasing has a novelist's touch, fitting prose narration of a private emotional moment. The te-form 見て chains the seeing as the cause of the blushing.