Modern day female jazz recommendations

Diane Schuur....any of her albums, especially the GRP ones (Grusin Rosen Production) are fantastically-recorded.
Her vocals are natural, unforced, and so realistically recorded, and her songs are wonderful to listen to. Wonderful orchestra backing that's exceptionally well-recorded.

You must try "New York".

There is an NPR issue CD called "Modern Jazz Divas" that I bought for some new exposure in this area and is worth a listen

Actually, the correct title is The New Jazz Divas

Check out Gaby Moreno on NPR first listen

Karrin Allyson (my latest female obssession outside of my wife). Check out "Ballads: Remembering John Coltrane" for straight jazz songs, and "Imagina" for Brazil/Bossa Nova songs. Both are to die for.