It doesn't matter if you're going to be 19. In fact, at least in the United States, you're considered "legal" in most states at 17. You're, first of all, putting this woman's career and lifestyle in danger. Is she married? Does she have a boyfriend? What would her family think? You seem to have little concern for her wellbeing and little knowledge of her personal situation.

Secondly, this woman is treating you and encouraging you in an entirely normal manner for a student-teacher relationship. You are just going to face rejection and embarrassment in the face of this woman if you pursue any sort of relationship with her. Part of being a good date is having the skills and empathy to recognize where you're wanted and to what degree. She has not made any sexual advances to you-- she clearly is unaware of your feelings and not seeking a relationship with you.