Translation:She will have missed the movie after dinner.
Hello Valerie, I am English and this whole lesson has me bemused! The above sentence would not be used in English, we would say something like "if she doesn't arrive until after dinner, she will miss the film", or if it is to be lost (which we couldn't know beforehand anyway!) "we may have lost the film if she doesn't arrive until after dinner", and I can only imagine that being said in a sarcastic way... Otherwise to use the term "missed' we would have to be using it in the past tense eg. "She didn't arrive until after dinner, so she missed the film". I know Duolingo wants to use the term "will have" and the past tense of a verb, but I am struggling at the moment to think of an appropriate sentence.
Interesting. I didn't know this tense existed in English until I learned it in French (futur parfait). I assume it's pretty much the same in all the Romance languages. I guess in French this sentence would be something like: J'aurai manqué de voir le filme… Without more context, it's pretty meaningless in both French and English, I guess.