She was heavily influenced by Dinah Washington and sounded somewhat like her, but yes, more nasally and with a quicker vibrato. For my taste she's absolutley fine. She's distinctive once you know her sound. A lot of her 60s and early 70s recordings have very good R&B session guys - like Curtis, Cornell Dupree, Chuck Rainey, Gordon Edwards, etc...and for me that's a big plus also.
Her earlier recordings with Johnnie Otis are tasty west coast early R&B.