My girlfriend said something to me yesterday that has me reevaluating everything

My(20m) girlfriend (20f) and I were making dinner for our friends and I said how it’s crazy that our friend is dating one of his best friends. They’ve all known each other since grade school. My girlfriend said that she thinks a lot of people date their best friends because they know them the best, they already know so much about each other, and they are comfortable with them, so its a good foundation for a relationship. I asked if that’s not what I am. I’ve known her since elementary school, and we’ve been best friends since grade school, and she said yeah but we became best friends when we were kids, and we don’t really know each other that well as adults. I’m also not her type and that I’m not attractive enough to be her boyfriend. I’m wondering now if she likes me, why does she like me. I’m her boyfriend, I’ve been her boyfriend for a year and a half, I don’t know how I’m supposed to be feeling right now.