I'm not a woman, but I feel the line is a bit blurry depending on the scenario. If it's genuinely unclear what this person is coming to you for, then I think this is a reasonable message to send. If you're already half way through hiring somebody, then it's clearly inappropriate.

Not propositioning people you're attracted to is a sure way to be alone in life; I tend to think it's fine as long as it doesn't interfere with your professional obligations.