Just tell her in a half-joking, but very smug way, "I cashed in a thief today, that worked as a part time fortune teller. She told me you're my soulmate." And that would be it! If she isn't interested in you, you still would have planted the thought in her mind, that you might be a suitable partner. And in case she is interested (which she is), you give her leeway for flirting.