Sharise's husband has Cortana on Windows 10, but it can't understand him. Leo says some microphones aren't Windows ready, and a special driver may be required for the microphone. They shouldn't be too far way from the microphone either. But they don't want to be too close, either. And make sure the volume isn't too high. They can train Cortana by reading sentences to it. That can be found in the settings. Cortana will get better over time.
Can Vista get updated to Windows 10? Leo says it depends on the hardware. Sharise should run the compatibility checker to see, and if so, $49 is a great deal to upgrade it.