Why did melisandre, the woman in red, tell jon snow after she failed to seduce him?

Melisandre is a character in the TV series Game of Thrones. She is a witch with strong ability of prophecy and divination. In the play, melisandre tried to have sex with jon snow and gave birth to the predicted "prince", but failed.

As for why melisandre said "You don't know anything, jon snow" to jon snow, it needs to be explained according to the plot. In the play, melisandre thinks that jon snow is the predicted "prince", but he doesn't have magical ability, so she thinks that he is not a real "prince", but just an ordinary person. Therefore, she might say this sentence to remind jon snow of his true identity and destiny, and let him know what he should really pursue.

It should be noted that the TV series Game of Thrones is adapted from a novel, so some plots and characters may be different.