It would be effective on most people, I think, regardless of gender. The "you were kinda cute" part flatters the ego, while being weak/soft enough a compliment to avoid making somebody suspicious that that is what you are doing. The "I was too shy to talk" suggests self-improvement and self-awareness, which are attractive qualities on their own; and then the message itself conveys confidence, which paired with that self-awareness and self-improvement, implies that the confidence is both genuine and earned, avoiding arrogance and hubris both.