Learn Spanish (Latin America): Al parecer, ella insinuó lo que realmente pasó. - Apparently, she hinted at what really happened.

While digressive markers like por cierto (by the way) shift the conversation to a side topic, al parecer (apparently) is used to express a deduction. It softens your statement by showing you are basing your claim on appearances or hearsay, rather than on established facts, without changing the subject.

Why do we use lo que here instead of just qué for the English word "what"?

In Spanish, qué is an interrogative word used for direct or indirect questions. In this sentence, "what really happened" acts as a noun clause meaning "that which really happened" or "the thing that really happened". Whenever "what" refers to a concept or unknown thing in a declarative statement rather than a question, you must use the relative pronoun lo que.

Could I use the imperfect tense insinuaba instead of the preterite insinuó?

Using the preterite insinuó means she made this hint as a single, completed action at a specific moment. If you swapped it for the imperfect insinuaba, it would change the meaning to suggest she was repeatedly dropping hints over a period of time, or that she was in the middle of hinting when something else happened.

Is it possible to place the adverb realmente at the very end of the sentence?