I expect you are correct Jack about it being in Eb minor, since leeneia mentions a range of Eb to Eb.

leeneia, Eb-Eb is squarely mid-range for a majority of 1st sopranos, which is a common voicing for choral type or "serious" music. All the above "just transpose it" advice is right on if the original key doesn't work for your people. The cited reasons for using 6 flats are true when they apply but if you can't sing a piece in the that key and you plan to sing it somehow or another, it really doesn't matter why it was put there. Just do whatcha gotta do.