As soon as the feeling became mutual, the spell would break.

That love she thought was oh so strong would vanish just like a bubble.

When the princess found out... She decided that even if the feeling was fake, she didn't want to lose it.

Rather than tell the prince, she would never see him again.

However—

The prince took her hand and confessed to her.

That's right. Their love had already become real a long time ago.