I am not against an intense relationship with an adult. I formed a very strong intellectual bond with an adult when I was 13.
But what is appropriate and not appropriate? Email, meeting in public, hanging out with friends?
I just caution that he take it slow. In 18 months he will have a different perspective. I know I did. And the legal system will, too.
If she gets obsessive, then it is a different ball game.
We all want to support our children's advanced intellectual (and in your son's case, emotional) ages. But this is possibly something different. I don't want to Google "pedophile" at work, but I suggest you do so.
I was approached by a pedophile when I was much younger. Pedophiles are predatory and exploitative. This woman does not sound like it. She is very open about her feelings and her relationship. Furthermore, the young man is functioning in an adult setting.
When I was 15, I went on a cruise with a friend's family. During the course of this cruise, a 23-year-old man decided he was in love with me. Why? Because of my intellectual maturity. That I could hold up conversations with him that very few people could.
Obsessive. The pedophile who was after me was the same way.
On the other hand, my mentor when I was 13 asked to meet my mom after we met at a video game parlor. She was there and they talked for a while. He was very careful to set boundaries and make sure he was above reproach. An adult will do that.
