。
All she could do at the sight was cry.
Literal
She [topic-は] that scene [target-に] just cry only was-polite.
~ばかり ('only, nothing but, just X') paired with a verb captures helpless or single-minded action: 'all she did was cry.' 泣くばかり literally 'only cry,' framing this as the sole reaction. ただ ('just, simply') reinforces the limitation. The polite past でした gives a narrative or reportorial flavor, distancing the sentence from raw emotion into recounted observation. The whole captures emotional overwhelm — when no other reaction is possible.