。
She suddenly walked off in tears.
Literal
She [topic-は] suddenly crying [while-ながら] walked-away [moving-away-ていった].
Two compound verbs and a directional auxiliary stack here. 立ち去る — 立つ ('stand') + 去る ('leave') — is the verb for someone deliberately leaving a place (it has a slightly literary edge over the everyday 出ていく). On top, ~ていく adds the directional sense of moving away from the speaker, both spatially ('went away') and narratively ('out of the scene'). The ~ながら on 泣く makes the crying simultaneous with the walking-away — she didn't cry first and then leave, or leave and then cry; the two unfolded together.