Learn Spanish (Latin America): Fue ella quien lo desmintió en el comunicado. - It was she who denied it in the statement.

Using fue (it was) and quien (who) creates what is called a cleft sentence. This structure is used to add strong emphasis. While Ella lo desmintió simply states a fact, Fue ella quien lo desmintió specifically highlights that she was the one who did it, rather than someone else.

Could I use que instead of quien in this sentence?

Yes, you can! Fue ella que lo desmintió is also correct and very common in everyday spoken Spanish. However, when the emphasized part of the sentence is a person, using quien (or quienes for multiple people) sounds a bit more precise and elegant.

Why is the first verb Fue (preterite) instead of Era (imperfect) or Es (present)?

In these emphasizing sentences, the verb ser usually matches the tense of the main action. Because the denying was a completed action in the past (desmintió, which is in the preterite tense), we use the preterite fue to match it.

What is the lo doing before desmintió?

lo is the direct object pronoun meaning 'it.' It refers to whatever rumor, claim, or accusation she is denying. In Spanish, this pronoun must go immediately before the conjugated verb.