Le Futur Anterieur after Quand

Question

After studying this lesson i took a C1 test.
I was given: Quand elle______________enfin au loto, elle sera heureuse.
I wrote:  Quand elle aura gagne enfin au loto, elle sera heureuse. (sorry I can't get the accent of the last e in gagne)
It was marked incorrect with the correction:  Quand elle gagnera efin au loto, elle sera heureuse.   
This doesn't seem to follow the pattern since first she will have won the loto and then she will be happy.  What am I missing here?

Accepted Answer

Bonjour Michele,
Both options with Le Futur Simple and Le Futur Antérieur are correct. However, there is a nuance:
- when using "gagnera" (Le Futur Simple), you are referring to 2 simultaneous actions.
- when using "aura gagné" (Le Futur Antérieur), you are referring to one action happening after the first one took place.
The "issue" with using Le Futur Antérieur here is the position of "enfin": with Le Futur Antérieur, "enfin" must be placed between "aura" and "gagné" - it cannot be placed after as in the test question.
However, thanks to your comment, we've now amended the test question to avoid any further ambiguity.
I hope this is helpful.
Bonne journée !