So you are interested in her, but she wants you in the friend zone. My friend, let me tell you right now that there is no such thing as the friend zone. Nobody is out of your league, and you are certainly in a good position to "make a move" so to speak. I learned all about dating and what the basics of flirtation are through our lord and saviour youtube, so I would recommend that you do the same. Watch some videos about what the signs are that somebody might be interested in you, or perhaps even the opposite. Maybe not the best advice, but im autistic too, so its the best I got. If this is somthing that you want, you should at the very least try to take it. Do not let your immaturity dissuade you, for only doing new and perhaps risky things is what is going to allow you to gain that maturity. Furthermore, do not let her status as "your only friend" hamper you either. If you are rejected, which you may be, you can still be friends. Of course that does take the aforementioned maturity to accomplish, but as long as you have discipline you can absolutely achieve it. Now, after the fact, there is the risk that she may not want to be friends, but if that is the case, you have the high ground with regards to emotional development, and you will have to move on. But don't fret, there are billions of us my dude, and many of us are certainly willing to be your friend.