I had a cat years ago that would "talk" to himself in the bathtub, and anywhere that there would be an echo. I think he liked the sound of his voice (thought himself one of the great tenors) so I wouldn't be concerned about that. Would definitely get her checked out by a vet, but I wouldn't necessarily worry about the singing if it doesn't sound like she's in discomfort. Maybe she wants to start a band.....?
