、。
On hearing the news, she cried as if her heart would break.
Literal
She [topic-は] that news [object-を] hearing [then-て], chest [subject-が] burst-tear [as-if-about-to-んばかりに] cried.
胸が張り裂ける ('chest bursts open') is a vivid idiom for overwhelming emotional anguish — the sense of being unable to contain grief, similar to English 'heart breaks.' Pairing it with ~んばかりに ('as if on the verge of, almost as if') gives the simile structure: she cried as if her heart was about to burst. This ~んばかり is the volitional ~ん (=~う) + ばかり ('only') = 'just-about-to,' a slightly literary pattern. 張り裂ける literally 'stretch + tear apart' is a powerful compound verb. The whole phrase belongs to dramatic, written narration.