Sorry got off topic there a bit. Yes ask her out. I was 4 years older than my first wife. I was out of highschool she was still in highschool, grade 12. She was very mature for her age, and way more mature than me.
. We got married but sadly life took us in different directions and we are no longer together. That was over 15 years ago. Found the love of my life now. Thing is, if you don't ask her out, you will never know what could have been. You ask her out, it may not work out, but then agian, I don't think you are looking for marriage, just going out with someone you like and have a fun time.
So speak to her parents, let them know of your intentions and ask her out. I wish boys would do this for my daughters but they don't. You got a good head on your shoulders, after all you are just going out, maybe a dinner or something. They say never a movie on the first date since you will not be doing alot of talking or communitcating, so a dinner and what ever else kids do these days now for fun.