Umm, Etta James was pure blues/r&b, not CW. Another vocalist who was one of the best of her genre.
First I heard of her was "Tell Mama", a killer up-tempo single in it's day (1968). Later I got into the rest of her catalogue. Superb quality throughout.
She was upset. But the Obama people knew that James was not well at the time of the inauguration (2008). She had been suffering from dementia and (supposedly) drug addiction issues and so they figured that it would be prudent to have Knowles do the song as Knowles had played her in the movie "Cadillac Records" recently (though Knowles looks nothing like James). Knowles did the song justice.