I would deal with it the same way I do with any teenager. Ask them to be mindful of who they are engaging with on a deep emotional level and why. To truly try to think about the experience and how much it really does change relational and emotional dynamics. That being curious is okay but try not give in to whims, but to contemplate and respond appropriately. I think that the emotional maturity of most teenagers is not developed enough to be engaged in those activities. That investing, that much of your self into another, is dangerous because it stunts your own personal growth when you start doing things that maybe you aren't confident about because you are curious or confused. I know it's easier said then done but I think it needs to be talked about. That being said I support my child's happiness over all. I just hope they don't confuse physical happiness for spiritual and emotional happiness.