Plenty of artists who can't sing sell records. Brittany Spears, anyone? Hell, most R&B acts of the last few years are garbage. A bunch of non-singing dancers...
I's not about being a WORLD CLASS singer (as if you'd even recognize one). Only envious haters bring up "singing" all the time. Some of the greatest artists in history were lightweight (or even poor) singers. You want singing, listen to opera, and not Pop or R&B music. It's always been about making GREAT TRACKS (by any means necessary) that people really, really like. And she's aleady made a bushel of them.