Even if Phaedra had known about Theseus and Nike, she still would have come on to him. He was hers, and always would be! And vice versa. They always found their way back to each other, even if it wasn't the most conventional of ways.
Phaedra gave him a look that clearly said what the hell? She laughed, "What are you talking about? You've never said no to me before." She moved closer to try and get her lips close to his, because he was clearly not thinking straight.