Consuelo is right on! It's all in the intonation.
I still use coquette - but then I am old and often "recidivist" in my word choices.
I think it would be more like "heart-breaker" if you meant a woman of any age who was pretty/beautiful/handsome; who had a "way about her" and who is a bit of a flirt either intentionally or not.
However, never meant as a woman of easy virtue!
We would say of a beautiful female child - one that is usualy smiling at you - "She will be a heart breaker when she grows up."