Eh... it IS a bit of a gap...

I look out for my female friends in college who are 19-20 who want to hang out with guys over 24 and I am the policeman There really is just too big a difference... sure she may be extremely mature for her age, but there is so much in life she does not know and cannot feel and internalize without time.

However, against my better judgement, I will say go for it! You really sound like you care about her; the biggest problem in age-gap relaitonships with a younger girl is that the guy only wants sex... and it doesn't sound like this is the case (it better not be or I take back everything I just said!) So, just go SLOW and CAREFULLY, but numbers are a silly thing to let get in the way of love. My ex was 2 years older than me (19-21 at the time) and that was such a HUGE deal to her and her family... ultimately was one of the factors in why we split I suppose... but I just thought it was oh so stupid to even mention that... I was every bit as mature as she was, I saw us as equals, but she always looked down on me like the 5th graders look at the 3rd graders on the bus or the playground... so I am a big advocate of age-difference relationships! If you are in love and both are happy, then what in the world can get in the way of that? Good luck with it!