It's normal for Asperger's to go undiagnosed, especially in girls. I wasn't diagnosed until I was 17. I think the diagnosis has been worth it, mostly because it helps me understand that my problems are legitimate, that my brain works differently, and that I'm not an inferior person because of it. I've also started therapy right after the diagnosis, which has helped me with my anxiety and depression. Plus, I get some accomodations at school, like testing in a quiet area. The only major downside for me is the cost of the evaluation and therapy, but I think if you can afford it it's absolutely worth getting evaluated.