All I can find in my files is the following - I haven't heard it, alas, hence I don't know if the info is accurate and if she's actually on "Blue Skies", singing with Rushing:
Count Basie Orchestra
September 11, 1948
Royal Roost, New York
Radio Broadcast
Clark Terry, Jimmy Nottingham, Harry "Sweets" Edison, Emmett Berry (tp) Bill Johnson, George Matthews, Ted Donnelly, Dicky Wells (tb) Bernie Peacock (as) Earl Warren (as,vcl-1) Wardell Gray, Paul Gonsalves (ts) Jack Washington (bs) Count Basie (p) Freddie Green (g) Singleton Palmer (b) Shadow Wilson (ds) Dinah Washington, Jimmy Rushing (vcl-2)
X-1
Futile Frustration
Good Bait
Moon Nocturne (-1)
Paradise Squat
Blue Skies (-2)
The King