Yaguchi Mari.
Note that the only one of these confirmed in the interview [which is not with Oda] is the first set. The other two have merely been speculated upon given their timing in the series and similarities.
Also, please keep in mind they were not voice actors for the movie. Movie 8 didn't have any famous talent attached to the voices (not that I'm aware of or that were advertised at least) which is why they took on those 4 to promote the movie.
It just so happens that Yaguchi would go on to voice the filler girl and sing the opening.