。
She translated it word by word.
Literal
She [topic-は] that [object-を] word-by-word translated.
一語一語 (ichi-go ichi-go) is a reduplicated noun-adverbial pattern — 一+counter doubled — meaning 'each word, word by word, one word at a time.' Same pattern gives 一日一日 ('day by day'), 一人一人 ('one by one, each person'), 一歩一歩 ('step by step'). Used adverbially without a particle, modifying the verb directly. The whole sentence captures painstaking, deliberate translation — likely contrasted with a freer or more idiomatic rendering. 翻訳する ('translate') is the standard Sino-Japanese verb for translation, distinct from 通訳する ('interpret, do oral translation').