You have not even mentioned that important fact. This means that you leave everything regarding feelings, broken hearts, morality and so on to her to decide or experience on her own. I went on a date with someone who was 28 when I was Age differences aside, she is moving into a life of her own. You might also be concerned if he were 17, given that what you are afraid of her getting hurt, pregnant, or growing up too quickly, or him being with her just for one reason can easily happen with a 17 year old boyfriend too.
The obligatory XKCD cartoon:
Age of consent reform
First, that "protection" is used for all physical activities. May 23, Though I don't think 19 year olds should go out prowling for 17 year olds, but if they started dating several years ago its no problem. Age of consent reform UK. But I would be careful in how you deliver your feelings. He does seem a very sensible person. Thank you for your interest in this question.