You're entitled to your opinion, just know that it's a very US-specific one and not shared outside of there. Henry and the woman he was dating are British, and in the UK (and the rest of Europe) she is socially considered an adult. The legal drinking age (not that it matters, but just to address your point) is 18.

Our attitudes towards sex are also very different here, we receive sex education from a young age, it's an openly discussed aspect of human life, and by 19 you're definitely considered old enough to be having an active sex life with another adult. There's nothing wrong with a young adult having a sexual relationship with someone like Henry who is clearly very attractive. I mention his attractiveness because it's far more likely that she just finds him hot rather than he is using money or coercing her.