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All she could do at the news was cry.
Literal
She [topic-は] that news [object-を] hearing [then-て] just cry [only-ばかり] was.
ただ~ばかり ('just X and nothing else') is a useful pattern for 'do nothing but X.' ばかり after a verb's plain form means 'only doing X,' and ただ ('just, only, simply') reinforces the exclusivity. The construction 泣くばかりだった ('was just crying') casts crying as her sole, helpless response — implying inability to do anything else. The flatness of the description matches the helplessness it describes.