It's a name coincidence methinks. Beyond the name and that both sing there aren't any connections that I see. And Keyes was an actress not a singer. She only sang like two songs total that we know of and one was "Begin Again" which Sinclair commissioned from his obsession with her that made him make the Sierra Madre revolve around her.
On the topic of Vera Keyes I have always been fascinated by her character. She perfectly personifies the old world in the desire of post-war culture to know more of the past, putting it on a pedestal as perfect but in reality it's a rotten fruit but then you realize by no fault of its own because post-war or pre-war; people are people.
God I love Dead Money.