"She is perfect."
Translation:Elle est parfaite.
This is a rule you will have to apply VERY often on Duolingo. In French, "c'est" (sing.) and "ce sont" (plural) are used in a large variety of expressions, when a pronoun (it, she, he, they) is subject of verb "être" and followed by a nominal group, ie: article (+ adjective) + noun. - it is + noun => c'est + article + noun - she is + noun => c'est + article + noun - he is + noun => c'est + article + noun - they are + noun => ce sont + article + noun
If you have not noticed it yet, Duolingo always favors "transparent" translations.
"Parfait" and "perfect" are close enough to not look for synonyms.
This translation is also the first hint provided when you hover on the word.
Of course, "perfect" can be a verb (perfectionner) and sometimes, in text translations you might use "idéal(e)" to translate "perfect", for example when you want to avoid repetitions.
But in lessons, there are no voluntary traps.
"Transparent"? I always get the feeling Duolingo is just being inconsistent. Putting in the wrong hints is like someone not telling you your shoelaces are untied so you'll trip and figure it out the hard way whereas someone else might simply point it out so you can correct yourself before you fall. I get the feeling that whoever is translating the French section of this website, falls in the former category.
The German lessons have way fewer of these "transparent" hints and far fewer complaints about the hints being traps so it can't be a Duolingo guideline unless someone over there hasn't gotten the memo yet.