Yeah, the perfect has an implication of a something happening before an event and usually when we use already there is the same idea. But it's not wrong this way, so I guess they do it as the perfect tense has not been taught in the target language yet.
She has already decided. BrE/AmE.
She already decided. (adverbs "already, yet, & just" allow use of simple past in AmE as an exception)
In Portuguese, could this also mean "She decided immediately" ?
Earlier, "já" was given as a possible solution for a sentence with "immediately" in English. I'm not sure but I think it was something like "Venha cá já !".
So maybe in this order : "Ela decidiu já" ? Or "já" as "at once, right now" can only be used with imperatives (kinda like in English, e.g. "Stop it already !")