I wouldn't think much of a couple aging 36 and 46, but a 21-year old (especially a guy... Regardless of even his opinion, I would not take his youth and time to grow away from him... I thought guys in their 20's were "immature" according to women ( I guess it''s different when SEX is involved) Most of those situations don't last cause when that 21year old sees a nice 18-22 year old walks by (especially if he's in college) it's curtains for the that older woman!he needs to embrace his youth, its trials and tribulations; not to mention college and career choices... People need to experience as much of the menu life has to offer before they know what their favorite meal is... NO way I would date a 21 year old no matter how mature she "claims" to be. I put up with their relationship...could have so chosen someone more mature...
I thought that since I was an attractive, fit, well-educated, financially and emotionally secure guy that I would have no problem finding a woman in her mid 30s to settle down with and start a family.
When I remember who I was when I was 21 compared to who I am now, I see 2 different people.
Age is not just a number - with time, we grow emotionally and evolve as a person with the things we experience throughout the years. In the past, I've dated guys that young; but that's as far as it would go. She must really yearn for those old "college" days???
I would be afraid of taking her away from her youth. If he's ready and understands how you feel and you openly express that, I don't see why it would be a problem.
Having her lose the relationship experiences that we all have as we grow older. Incidentally, our relationship didn't end because of the age difference.