I believe people have already brought up this argument in the past, but what are the arguments against why forking new bitcoins won't devalue the currency? Lets

I believe people have already brought up this argument in the past, but what are the arguments against why forking new bitcoins won't devalue the currency? Lets say one day Lady GaGa decides to start her own bitcoin, would that in anyway devalue the current bitcoin network if everyone instead decides to start mining Lady GaGa bitcoins?