I would consider K Michelle on. She has dropped 3 albums. While everyone else is still trying to get the label to give them a second one
But to keep in line with the premise of the thread it is rather weird. Look at what Beyoncé and Rihanna are doing... You would think labels would put more resources into Female R&B.
I do think the main reason that R&B lost its standing is Rap got so big and now people mostly want to hear rap
It's hard for a lot of these Female singles to make songs like Formation, Drunk in love, work, needed me that fit right in with a mostly rap playlist and not destroy that mood