I've been thinking about the "she will have gone"/"she will have gone away" question, and it seems to me that if one were translating from English to Italian, "she will have gone" would have to be translated "sara andata VIA," but in translating from Italian to English, it would be correct (and more akin to what native English speakers might say) to say "she will have gone" without including "away" since most English speakers would know that "away" is implied, whereas, as one commenter notes, in Italian, "via" would be necessary. I am a little bothered when, as a translator, I try to give the correct English usage and Duo doesn't accept it.
Away just adds extra detail to the sentence: simply saying "gone" COULD mean "gone away", but it could also mean that she has gone somewhere specific, whereas away implies that it is unknown or unimportant to where she went. "Gone" could also mean more like "done" (as in: "who goes next in the competition?"), or it could even refer to death in this context.
As a native English speaker, I know that there are definitely occasions when I would use "gone away" and occasions when I would simply use "gone". It rather depends on the context + of course, Duolingo naturally tends to prefer literal translations.
You may have since learned this but it is "she" because "andata" is used in the conjugation. If "andato" had been used it would have been "he". You can check this here http://www.italian-verbs.com/italian-verbs/conjugation.php?parola=andare under Futuro Anteriore.
Maybe DL has added "away" to make you remember that in Italian we seldom use "andare" alone. In English a "he's gone" is sufficient. In Italian a simple "E' andato" would be a little puzzling. We usually specify where he's gone. And if we don't want to specify it, and we want to say that he is no more here only, then we use "via", away.
You call your friend's home
Could I speak to Tom ?
Sorry, he's gone.
Here, an italian would always say "Spiacente, è andato VIA".