Hi aspiebirder. You didn't state whether she is AS or NT and you didn't say whether she knows you are AS or not.
First let me say I am an NT woman an I admire that you have self evaluated and have seen there is an issue and are willing to try and help fix it.
With that said I will go with she is not an AS and you have either not told her you are AS or explained to her what that means exactly.
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If you two are still speaking I would let her know if you haven't already that you are AS and what that means. Tell her that you are interested in what she likes, her interests, and what her feelings are but sometimes you just dont know how to ask her or bring it up. Most NT girls will say Oh I didn't know that and all you have to do is say is what happened with you today or how are you feeling? Then you could say it would really help you if she would tell you herself even if you dont ask her. Explain that is not that you do not care you just dont know how to ask her. If she is a nice girl she will just say ok an do it. But you also have to try and remember to ask to. So put a sticky note on your computer, a notebook, or a note in your locker anywhere you can to remind you to ask her how she is doing if it does not come natural to you.
Most NT girls want you to ask about how they are doing, what they like, what they dont like, and what interests them. If you are willing to try and learn how to do this it will help you out greatly in the future with all relationships with girls. You may not need this because you are AS but an NT girl does. So this would be a good time to learn the skills you would need for liking girls in the future.
I can only speak for me but I would like if a boy said to me what you said above and told me that truth (that last year it seemed like you were best friends and now you are not and you were wondering if there is anyway you could talk more and be better friends)
If you are comfortable tell her you are interested in hearing about the things she likes but you have a hard time asking her sometimes. Tell her that it would help you out alot if she helped you by starting the conversation first. Tell her you like it when she she tells you how her day was or how she is feeling.
When she is talking it is always good to acknowledge what she is saying and let her know you heard her. You can say something like yes, ok, I hear you, or even nod your head.
The only way to get close to someone is be open and honest and share your feelings. I know because I am NT and my bf is AS that he and I dont always have the same interests but he cares enough about me to listen to me and try to understand.
My bf is AS and it makes me care about him more because it does not come naturally to him wither but he tries very hard. It makes me care about him more that he tries so hard to make me happy.
Just remember though if you tell her about you and she is not accepting, not nice, or understanding then she is not the right girl for you. I know it will hurt alot but you need to know there are nice girls that care about other people and will care about you. They realize all of us are different in some way.
Never her let her humiliate you, make fun of you, or hurt you intentionally.
Trust me when I say there are many girls out there that would love and feel very lucky to have you. If I have answered incorrectly because I dont have all the information please feel free to write again or send me a message. Good luck