Why did Helen leave with Paris?

According to the myth, When Paris made his choice of bride, Aphrodite had Eros prick her with an arrow, making her fall in love with Paris.

More likely, Helen was disenchanted with Menelaus (because she didn't choose him herself, her father did), and chose to run off with the much younger Trojan prince. This view is presented in the movie Troy, and I think it presents a more accurate and realistic version of what actually happened.