Obviously communication is key, as with any relationship. Listening is just as important. Listen to her feedback, is it sincere, or is she buying time with some irrelevant response. Is she attempting to resolve your concerns? Or hoping they'll just go away. She may be beautiful, and everything you currently are seeking in a young woman, but is she mature and stable....
Is 23 too young to propose? I proposed when I was 23, married at 24, first born at 25, then again at 28 and 31!! LOL.....BE READY for marriage.
I think 20 is too young to comprehend exactly what a life commitment is. Have you both had all your "single", non-committed fun yet? Where/what are her closest friends doing with there lives, any of them settleing down?
Its kind of funny. I was the first of all my buddies to settle down and start a family. They eventually followed suit, but now there in there 40's with 5 and unders, while mine are going to college or highs school..(OK my youngest is in 7th grade, a girl, and has me totally wrapped) Slight thread jack...............sorry
Anyway, if its mean to be, this will work out with a little effort on both parts. Your both still young, and in love i suppose. Remember, with love, age, and respect, comes maturity. Lets see
if she has what it takes.....