。
She left without saying a word.
Literal
She [topic-は] one-word even didn't-say [without-ずに] went-out.
ひとことも~ない is a near-fixed expression meaning 'not a single word,' with も intensifying the negation: even one word was not said. ~ずに is the literary or written-style alternative to ~ないで for 'without doing': 言わずに ('without saying') reads slightly more elevated than 言わないで, and is preferred in narrative prose. 出て行く is a compound combining 出る ('exit') and 行く ('go'), giving directional 'go out and away (from the speaker's perspective)' — distinct from 出てくる, which would frame the motion as coming toward the speaker.