Whoever is spinning on my turntable is my favorite … for today! In a pinch my gut answer would be Ella. It’s a shame you rule out the female artists of Grand Opera. The People’s Diva Renee Fleming has lent her vocal gift to genres well beyond the opera stage. She’s not the only diva to do so.
I encourage you to open your horizons just a bit. You are selling yourself short IMO assuming the world class singers of opera only do Wagner. Just not so.