@AlfonsoTheUnrepentant
Why would dancers need bigger breasts unless they are dancing burlesque or private shows? Big breasts are seen as a disadvantage in most kinds of dance.
I'm guessing that either they wanted to re-use a costume from a previous production rather than create a brand new one, or they were going to make a brand new costume but wanted it useable in subsequent productions.
So they might have asked the dancer if they could wear falsies either to fit the costume they had, or so that the costume could be fitted to any subsequent dancer with larger breasts.
A costume for a female role fitted to a male-shaped dancer is probably only going to be re-usable for other male-shaped dancers in female roles.