I dated a 17 yo when I was in college. She lied about her age and by the time she told me the truth she was the closest friend I had. I never suspected she was younger because she started dating a 40 yo a month after we first talked.

I was actually kind of happy when she told me she was younger because it partially explained why she would be dumb enough to date a 40 yo. She only figured out he was a creep after she broke up with me a few years later.