Speaking from personal experience here, it is a bit of a difficult one to get a yes no answer too. I have had this problem occur to me quite recently (within the last twelve weeks) and I made the desicion to tell the person I liked that I liked her. This didn't all go according to plan as she wasn't looking for a relationship and because of that I got rejected. In your case, I would suggest a few things
1. If you can take a negative response (no, I don't want a relationship) then go for it. What the others say is right and you will never even know if you don't ask.
2. If you aren't sure how you would cope, speak to someone you trust about it all to see what their opinion is. Obviously they then have to keep what you tell them secret and only tell someone you trust not to tell her about it. It does help though if the person who you tell about it knows her and is friends with her as it might give you an insight into what her perspective on it is.
3. I know you said you haven't told your parents about it but, speaking from personal experience here, they might be able to give you the confidence you need to ask. If things do go wrong chances are they will find out and it will be easier for you to deal with a either response if they know the situation as they can best support you through it.
4. If you need to sort out a safe location to ask so that you both are comfortable enough so that it is easier to ask, speak to your teacher or an autism specialist from your school/college. They might be able to provide you with a space and, once again, if things go wrong they can step in to help the two of you out
If I had to give an opinion right at this moment, I would say go for it. You will never know unless you ask. For all you know, the same might be happening on her end of things and it might be a lot less difficult if it is. I wish you the best of luck
SRT456